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Solving linear equations with variable on both sides - class-X

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The ratio of the present age of Manoj to that of Wasim is $3:11$. Wasim is $12\ yr$ younger than Rehana. Rehanas age after $7\ yr$ will be $85\ yr$. What is thepresent age of Manojs father, who is $25\ yr$ older than Manoj?

  1. $43\ yr$

  2. $67\ yr$

  3. $45\ yr$

  4. $69\ yr$


Correct Option: A
Explanation:

 the present age of Wasim $=11x$

 present age of Manoj $=3x$

 present age of Rehana $=11x+12$
 present age of Manoj's father $=3x+25$

 after $7$ years, Rehana's age is $85$ years. 
 $11x+12+7=85$
 $ 11x=66$
 $x=6$
 
age of Manoj's father $=3 \times  6 + 25 = 43$ years. 

The sum of three consecutive odd numbers is $38$ more than the average of these numbers. What is the first number

  1. $13$

  2. $17$

  3. $19$

  4. Data inadequate

  5. None of these


Correct Option: B
Explanation:
let $'a'$ be the first odd number

As per Question

$ a+a+2+a+4 = 38 +\dfrac{a+a+2+a+4}{3}$

$ \Rightarrow 3a+6 = 38+a+2 $

$ \Rightarrow 2a = 34$

$ \Rightarrow a = 17 $

Solve $3x-450=2x-240$.

  1. $210$

  2. $230$

  3. $220$

  4. $200$


Correct Option: A
Explanation:

We have,

$3x-450=2x-240$

$3x-2x=450-240$

$x=210$

Hence, this is the answer.

The age of  manoj  after $15$ years is $4$ times the age of that $15$ years before. His present age is 

  1. 10 years

  2. 15 years

  3. 20 years

  4. 25 years


Correct Option: D
Explanation:

Let the present age of manoj be $x$ years.

According to the question,
$x+15=4(x-15)$
$x+15=4x-60$
$3x=75$
$x=25$ years


The denominator of a rational number is greater from its numerators by 10. If the numerators is increased by 19 & the denominator is decreased by 1. The number obtained is $\dfrac { 3 }{ 2 } $. Find the rational number.

  1. $\dfrac{1}{11}$

  2. $\dfrac{7}{17}$

  3. $\dfrac{11}{21}$

  4. None of these


Correct Option: C
Explanation:

Let the numerator be $x$.

$\Rightarrow$  Then, denominator will be $=x+10$
According to the question,
$\Rightarrow$ $\dfrac{x+19}{x+10-1}=\dfrac{3}{2}$

$\Rightarrow$  $\dfrac{x+19}{x+9}=\dfrac{3}{2}$

$\Rightarrow$  $2(x+19)=3(x+9)$

$\Rightarrow$  $2x+38=3x+27$

$\Rightarrow$  $x=38-27$

$\Rightarrow$  $x=11$

$\Rightarrow$  The required rational number $=\dfrac{x}{x+10}=\dfrac{11}{11+10}=\dfrac{11}{21}$

If
$\displaystyle \frac{a}{3y}\, +\, \frac{3b}{x}\, =\, 1$ and $3a + 1 = 2a + 2 $
x = 5, find the value of y.

  1. 0.83333

  2. 2.5

  3. 2.0

  4. 1.5


Correct Option: A

Given that $\displaystyle {\frac{-6p\, -\, 9}{3}\, =\, \frac{2p\, +\, 9}{5}},$ find the value of p

  1. -4

  2. -2

  3. 3

  4. 5


Correct Option: B
Explanation:

We shall Apply cross multiplication method.

$\dfrac { -6p-9 }{ 3 } =\dfrac { 2p+9 }{ 5 } \ \Longrightarrow 5\times \left( -6p-9 \right) =3\times \left( 2p+9 \right) \ \Longrightarrow -30p-6p=27+45\ \Longrightarrow -36p=72\ \Longrightarrow p=-2$
Ans- Option B.

A boy is now $a$ years old and his father is $5a$ years old. How old will the father be when the boy is $3a$ years old? How old was the father when the boy was born?

  1. $7a, 4a$ years

  2. $4a, 10a$ years

  3. $12a, 3a$ years

  4. $15a, 3a$ years


Correct Option: A
Explanation:

Difference of the age of boy and father $=5a-a=4a$

$\therefore$ The father's age when the boy is $3a$ years old $=3a+4a=7a$
When the boy was born, then the father's age $=4a$.

A boy was asked to multiply a given number by $\displaystyle \frac{8}{17}$. Instead, he divided the given number by $\displaystyle \frac{8}{17}$ and got the result $225$ more than what he should have got if he had multiplied the number by $\displaystyle \frac{8}{17}$. The given number was

  1. $8$

  2. $17$

  3. $64$

  4. $136$


Correct Option: D
Explanation:

Let the given number be $x$


According to problem, 

$ 225 + x(\cfrac {8}{17}) = \cfrac{x \times 17}{8}$
$ 225 = \cfrac{17x}{8} - \cfrac{8x}{17}$
$ 225 = \cfrac {225x}{136}$
$ x=136$

Water flows at the rate of $10$ metres per minute from a cylindrical pipe $5$ mm. in diameter. The time taken to fill up a conical vessel, whose diameter at the base is $40$ cm and depth $24$ cm., is

  1. $55$ minutes

  2. $52$ minutes $1$ sec

  3. $51$ minutes $12$ sec

  4. $48$ minutes $15$ sec


Correct Option: C
Explanation:
Time taken = Volume flown / Volume flown in 1 min

$=\dfrac{\frac{1}{3}P _i(20)^2 \times 24}{P _i \times \frac{2.5}{10} \times 1000}$

$=\dfrac{3200P _i}{62.5P _i}$

$=51 min. 12 sec$

In a caravan  in addition to 50 hens there are 45 goats and 8 camels with some keepers.  If the total number of feet be 224 more then the number of heads in the caravan, find the number of keepers

  1. 5

  2. 8

  3. 10

  4. 15


Correct Option: D
Explanation:

If the number of keepers be x  then total number of feet = $2  \times 50 + 4   \times 45 + 4 \times  8 + 2x$
$=2x + 312$
Total number of heads = $50 + 45 + 8 + x$
$=103 + x$
$\displaystyle \therefore 2x+312=103+x+224$ or$x = 15$

The solution of $\displaystyle 2^{3x-6} =\frac{1}{8^x}$ is---

  1. 1

  2. $\displaystyle \frac{4}{2}$

  3. 4

  4. -1


Correct Option: A
Explanation:

$\displaystyle 2^{3x-6} =\frac{1}{8^x} ; 2^{3x-6}$
          $\displaystyle = 2^{-3x}$
$3x - 6 = -3x ; x = 1$

Solve $1.32y + 0.02y = 1.19 + y$.

  1. $-\dfrac{7}{2}$

  2. $3\dfrac{1}{2}$

  3. $\dfrac{7}{4}$

  4. $-3\dfrac{1}{4}$


Correct Option: B
Explanation:

$1.32y+0.02y=1.19+y$

$\Rightarrow 1.34y=1.19+y$
$\Rightarrow 0.34y=1.19$
$\Rightarrow y= \dfrac {1.19}{0.34}$

$\Rightarrow y= \dfrac {119}{34}$

$\Rightarrow$ $ y= \dfrac {7}{2}$ $= 3 \dfrac{1}{2}$

In a family, each daughter has the same number of brothers as she has sisters and each son has twice as many sisters as he has brothers. How many sons are there in the family?

  1. $2$

  2. $3$

  3. $4$

  4. $5$


Correct Option: B
Explanation:

Let $d$ and $s$ represent the number of daughters and sons respectively.
Then, we have :
$d - 1 = s$ and $2 \left(s - 1\right) = d$.
Solving these two equations, we get: $d = 4$, $s = 3$.

A number consists of two digits whose sum is $9$. If $27$ is added to the number, its digits are interchanged. Are the given steps to find the number true?
Step $1$: Let the unit's digit be x
Step $2$: Then, ten's digit $=(9-x)$
$\therefore$ number $=10\times (9-x)+x\Rightarrow 90-10x+x=(90-9x)$
Step $3$: Adding $27$ to the number $90-9x$ we get $117-9x$
Step $4$: Number with digits interchanged is $10x+(9-x)=9x+9$
Step $5$: $117-9x=9x+9$ 
Step $6$: Therefore unit's digit$=6$ and ten's digit $=3$
Step $7$: Hence the number $=36$.

  1. Yes

  2. No

  3. Cannot say

  4. Only step $1$ and $2$ are correct


Correct Option: A
Explanation:

All the given steps to find that unknown number are True.
Hence the option A is the correct answer.

When a number is reduced by $4$, it becomes $80\%$ of itself. Find the number.

  1. $20$

  2. $30$

  3. $40$

  4. $50$


Correct Option: A
Explanation:
Let the Number be $X$
Number is reduced by $4$ i.e. $X-4$.
Now number becomes $80 \% $ of itself
$X-4 =  80\%  $ of $X$
$ \Rightarrow X-4 = \dfrac{80}{100}\times X$
$ \Rightarrow X-4 = 0.8 X$
$ \Rightarrow 0.2X=4 $
$ \Rightarrow X=20 $
The number is $20$.

A number is multiplied by $2\displaystyle\frac{1}{3}$ times itself and then $61$ is subtracted from the product obtained. If the final result is $9200$, then the number is __________.

  1. $36$

  2. $63$

  3. $67$

  4. $37$


Correct Option: B
Explanation:

Let the number is $x$

According to given question, we have
$ x\times \dfrac{7x}{3} -61 = 9200$

$\Rightarrow \dfrac{7x^2}{3}=9261$
$\Rightarrow x^2=9261\times  \dfrac{3}{7}$
$\Rightarrow x^2 =3969$
$\Rightarrow x=\sqrt{3969}$
$\Rightarrow x=63$

The two consecutive multiples of $3$ whose sum is $51$ are __________.

  1. $24, 27$

  2. $20, 31$

  3. $40, 11$

  4. $25, 26$


Correct Option: A
Explanation:

Lets say $x$ is the multiple of $3$

Next consecutive multiple of $3$ will be $(x+3)$
Given sum is $=51$
$\Rightarrow x+x+3=51$
$\Rightarrow  2x=48$
$\Rightarrow x=24$
Two consecutive multiples of $3$ are $24,27$.

$\displaystyle\left(\displaystyle\frac{2}{3}\right)^{rd}$ of a number when multiplied by $\displaystyle\frac{3}{4}$ of the same number make $338$. The number is ___________.

  1. $18$

  2. $24$

  3. $36$

  4. $26$


Correct Option: D
Explanation:

Let the number is $x$

Thus according to given problem, we have
$\dfrac{2}{3} x\times  \dfrac{3}{4} x= 338$
$x^2=338\times 2$
$x^2= 676=26^2$
$x=26$
Therefore, the number is $26$.

A number is multiplied by half of itself and then $32$ is added to the product, if the final result is $130$, then find the original number.

  1. $4$

  2. $7$

  3. $5$

  4. $14$


Correct Option: D
Explanation:

Let the number be $x$

According to given question, we have
$x\times  \dfrac{x}{2} +32=130$

$\Rightarrow \dfrac{x^2}{2}=98$
$\Rightarrow x^2=196$
$\Rightarrow x=14$

Therefore, the number is $14$.

If $\left(\displaystyle\frac{2}{3}\right)^{rd}$ of a number is $20$ less than the original number, then the number is ___________.

  1. $60$

  2. $40$

  3. $80$

  4. $120$


Correct Option: A
Explanation:

Let the number is $x$

Therefore, $x-\dfrac{2}{3}x =20$
$\Rightarrow \dfrac{1}{3}x=20$
$\Rightarrow x=60$
Therefore, the  number is $60$.

A lady reaches her office $20$ minutes late by traveling at a speed of $20$ km/h and reaches $15$ minutes early by traveling at $30$ km/h. By how much time will she be early or late if she travels at $25$ km/h?

  1. $1$ minute early

  2. $5$ minutes early

  3. $1$ minute late

  4. $5$ minutes late


Correct Option: A
Explanation:

Let the distance of the office be $x$ km


Time taken at $20 km/hr = \dfrac{x}{20}hrs$

Given that she reaches $\dfrac{20}{60} = \dfrac{1}{3} hrs$ late

Time taken at $30 km/hr = \dfrac{x}{30}hrs$

Given that she reaches $\dfrac{15}{60} = \dfrac{1}{4} hrs$ early

$\therefore \dfrac{x}{20} - \dfrac{x}{30} = \dfrac{1}{3} + \dfrac{1}{4}$

$\Rightarrow x = 35km$

Time taken at $30km/hr = \dfrac{35}{30}\times 60 = 70$ minutes

Time taken at $25 km/hr = \dfrac{35}{25}\times60 = 84$ minutes

So travelling at $25 km/hr$ she reaches $70+15-84 = 1$ minute early

The average age of $3$ sisters is $15$. If the ages of $2$ sisters are $12$ years and $15$ years, the age of the third sister is-

  1. 21 years

  2. 17 years

  3. 18 years

  4. 16 years


Correct Option: C
Explanation:

Let the ages of sisters be $x,y,z$


Given that

$\Rightarrow \dfrac{x+y+z}{3}=15$

$\Rightarrow x+y+z=45$

Given that $x,y=12,15$

$\Rightarrow 12+15+z=45$

$\Rightarrow z=18$

Therefore, age of third sister is $18 years$

The difference of two numbers is $72$ and the quotient obtained by dividing one by the other is $3$. Find the numbers.

  1. $36$ $and$ $108$

  2. $16$ $and$ $88$

  3. $63$ $and$ $135$

  4. $\text{none}$


Correct Option: A
Explanation:

$Let\>the\>numbers\>be\>x\>and\>y,\>then\>x-y=72\\and\>(\frac{x}{y})=3\\or\>x\>=\>3y\\\therefore\>3y-y=72\\2y=72\\\therefore\>y=36,\>then\>x\>=\>108$

In an orchard, $\dfrac{1}{5}$ are orange trees, $\dfrac{3}{13}$ are mango trees and the rest are banana trees.  If the banana trees are $148$ in number, find the total number of trees in the orchard.

  1. $252$

  2. $360$

  3. $260$

  4. $352$


Correct Option: C
Explanation:

$let \>total \>number\> of \>trees=x \\then \>banana\> trees =148\\x-(\frac{x}{5})-(\frac{3x}{13})=148\\(\frac{65x-13x-15x}{65})= 148\\\therefore x= (\frac{148\times 65}{37})=260$

At present anil is $1.5$ times of purvis age. $8\ yr$ later, the respective ratio between Anil and Purvis ages will be $25:18$. What is Purvis present age?

  1. $50\ yr$

  2. $28\ yr$

  3. $42\ yr$

  4. $36\ yr$


Correct Option: B
Explanation:
Let Present age of Purvis is $x$ then, Age of Anil will be $1.5x$
 After $8 yr$,
                   Age of anil $=1.5x+8$ And Age of Purvis $=x+8$
             $\dfrac{25}{18}=\dfrac{1.5x+8}{x+8}$
                        $x=28$
 So Age of Purvis $=28 yr$

Solve for $x : \dfrac { x + 2 } { 6 } - \left[ \dfrac { 11 - x } { 3 } - \dfrac { 1 } { 4 } \right] = \dfrac { 3 x - 4 } { 12 }$

  1. $\dfrac { 6 } { 11 }$

  2. 10

  3. 14

  4. 11


Correct Option: D
Explanation:
$\dfrac{x+2}{6}-\left[\dfrac{11-x}{3}-\dfrac{1}{4}\right]=\dfrac{3x-4}{12}$

$\Rightarrow \dfrac{2(x+2)}{12}-\left[\dfrac{4(11-x)}{12}-\dfrac{3}{12}\right]=\dfrac{3x-4}{12}$

$\Rightarrow 2x+4-[44-4x-3]=3x-4$

$\Rightarrow 2x+4-44+3+4x=3x-4$

$\Rightarrow 6x-37=3x-4$

$\Rightarrow 3x=33$

$\Rightarrow x=11$.

Seven times a two digit number is equal to four times the number obtained by reversing the order of digits. Find the number, if the difference between its digits is $3$. 

  1. $14$

  2. $25$

  3. $36$

  4. $47$


Correct Option: C
Explanation:

Let one's digit be $x$ and the tens be $x-3$


Number = $10(x-3) +x$ 

Reversed no. = $10x +x-3$ 

$ 7(10(x-3) +x) = 4(x-3 +10x)\ 70x -210 + 7x = 4x -12 +40x\ 33x = 198\ x = 6$ 

Number = $36$

Solve: $\displaystyle \frac{2x\, +\,1}{10}\, -\, \frac{3\, -\, 2x}{15}\, =\, \frac{x\, -\, 2}{6}$.


Hence, find y, if $\displaystyle \frac{1}{x}\, +\, \frac{1}{y}\, +\, 1\, = 0$.

  1. $\displaystyle x\, =\, -\frac{7}{5}; \, y\, =\, -\frac{7}{2}$

  2. $\displaystyle x\, =\, -\frac{2}{5}; \, y\, =\, \frac{7}{2}$

  3. $\displaystyle x\, =\, -\frac{6}{5}; \, y\, =\, -\frac{7}{2}$

  4. $\displaystyle x\, =\, -\frac{12}{5}; \, y\, =\, \frac{7}{2}$


Correct Option: A
Explanation:

$ \dfrac {2x + 1}{10} - \dfrac {3-2x}{15} = \dfrac {x-2}{6} $

On taking LCM and simplifying, we get

$ \dfrac {6x + 3 - 6 + 4x}{30} = \dfrac {x - 2}{6} $

$ => \dfrac {10x - 3}{30} = x - 2 $


$ => 10x - 3 = 5x - 10 $

$ 5x = -7 $

$ x = -\dfrac {7}{5} $

Now, substituting x in $ \dfrac {1}{x} + \dfrac {1}{y} + 1 = 0 $, we get

$ - \dfrac {5}{7} + \dfrac {1}{y} + 1 = 0 $

$ => \dfrac {1}{y} = - 1 + \dfrac {5}{7} =  - \dfrac {2}{7} $

$ => y = -\dfrac {7}{2} $

An altitude of a triangle is five-third the length of its corresponding base. If the altitude is increased by $4 cm$ and the base is decreased by $2 cm$, the area of the triangle remains same. Find the base and the altitude of the triangle.

  1. The base of the triangle is $12 cm$ and altitude is $20 cm$.

  2. The base of the triangle is $4 cm$ and altitude is $34 cm$.

  3. The base of the triangle is $16 cm$ and altitude is $12 cm$.

  4. The base of the triangle is $8 cm$ and altitude is $32 cm$.


Correct Option: A
Explanation:
Let the base of the triangle be $x$ cm. 
Then, the altitude of the triangle $=\cfrac { 5x }{ 3 } $
So, area of the triangle $=\cfrac { 1 }{ 2 } \times base\times altitude$
$=\cfrac { 1 }{ 2 } \times x\times \cfrac { 5 }{ 3 } x\\ =\cfrac { 5 }{ 6 } { x }^{ 2 }$        ...(1)
On increasing the altitude by $4 cm$ and the decreasing base by $2 cm$, the area remains the same.
Therefore, $\cfrac { 1 }{ 2 } \times (x-2)\times \left( \cfrac { 5x }{ 3 } +4 \right) =\cfrac { 5 }{ 6 } { x }^{ 2 }$       ...[using (1)]
$\Longrightarrow \cfrac { 1 }{ 2 } \times (x-2)(\cfrac { 5x+12 }{ 3 } )=\cfrac { 5 }{ 6 } { x }^{ 2 }$
$ \Longrightarrow (x-2)(5x+12)=5{ x }^{ 2 }$
$ \Longrightarrow 5{ x }^{ 2 }-10x+12x-24=5{ x }^{ 2 }$
$ \Longrightarrow 2x-24=0$
$ \Longrightarrow 2x=24$ or $x = 12$.
 Now, altitude of the triangle $=\cfrac { 5x }{ 3 } =\cfrac { 5\times 12 }{ 3 } =20 cm$
Hence, the base of the triangle is $12 cm$ and altitude is $20 cm$.

Neglecting air resistance, the upward velocity of the water in the stream of a particular fountain is given by the formula $v = -32t + 28$, where $t$ is the number of seconds after the water leaves the fountain. While going upward, the water slows down until at the top of the stream, the water has a velocity of $0$ feet per second. How long does it take a droplet of water to reach the maximum height?

  1. $0.825$ seconds

  2. $0.925$ seconds

  3. $0.875$ seconds

  4. $0.975$ seconds


Correct Option: C
Explanation:

Given, $v = -32t + 28$
It is mentioned that at the maximum height, the velocity of water is $0$ feet per second.
Therefore, final velocity $(v) = 0$. 
$\Rightarrow 0=-32t+28$

$\Rightarrow 32t=28$      
$\Rightarrow t=\cfrac { 28 }{ 32 } =0.875$ seconds

Twelve years hence a person will be four times as he was twelve years ago, then his present age is

  1. $20$ years

  2. $25$ years

  3. $28$ years

  4. $30$ years


Correct Option: A
Explanation:

Let his present age be $x$
According to problem
$\Rightarrow\;x+12=4\;(x-12)$
$\Rightarrow\;-3x=-48-12$
$\Rightarrow\;3x=60$
$\Rightarrow\;x=20$ years.

A father is at present three as old as his son . Five years back he was four times as old as his son.  Find the age of his son

  1. 12 years

  2. 15 years

  3. 18 years

  4. 20 years


Correct Option: B
Explanation:

Present age of the son is 'x' years his father's age is 3x
Five year ago:
Son's age = x - 5 and father's age = $3x - 5$
$\displaystyle \therefore 3x-5=4(x-5)$ or x = 15

If the sum of four consecutive even integers is $212$, what is the value of the second even integer?

  1. $50$

  2. $51$

  3. $52$

  4. $53$


Correct Option: C
Explanation:

Let the four consecutive even numbers be $x, x + 2, x + 4$ and $x + 6$.

Therefore, $x + x + 2 + x + 4 + x + 6 = 212$
$4x + 12 = 212$
$4x = 212 - 12$

$4x = 200$ (Divide both sides by $4$)
$x = 50$

The second number be $x + 2$

So, the second number is $52$.

If the sum of four consecutive odd integers is $400$, what is the value of the first odd integer?

  1. $95$

  2. $96$

  3. $97$

  4. $98$


Correct Option: C
Explanation:

Let the four consecutive odd numbers be $x, x + 2, x + 4$ and $x + 6$.
Therefore, $x + x + 2 + x + 4 + x + 6 = 400$
$4x + 12 = 400$
$4x = 400 - 12$
$4x = 388$  (Divide both sides by $4$)
$x = 97$
The first number be $x$ 
So, the first number is $97$.

If the sum of four consecutive integers is $110$, what is the value of the third consecutive integer?

  1. $26$

  2. $27$

  3. $28$

  4. $29$


Correct Option: C
Explanation:

Let the four consecutive numbers be $x, x + 1, x + 2$ and $x + 3$.
Therefore, $x + x + 1 + x + 2 + x + 3 = 110$
$4x + 6 = 110$
$4x = 110 - 6$
$4x = 104$   (Divide both sides by $4$)
$x = 26$
The third number be $x + 2$ 
So, the third number is $28$.

The sum of a $2$ digit number and the number obtained by reversing its digits is $154$. If the digits differ by $4$, find the number.

  1. $95$

  2. $73$

  3. $84$

  4. $62$


Correct Option: A
Explanation:
Let two digit number $=ab=10a+b$
Sum of number and reversed number $=154$
$(10a+b)+(10b+a)=154$
$a+b=14$
difference between digits$=\left|a-b\right|=4$
$a-b=\pm 4$
$(a+b=14)+(a-b=4)=2a=18$    $a=9,b=5$
$(a+b=14)-(a-b-4)=2a=10$      $a=5,b=9$
$\therefore   \text {Number}=95 (or)59$

Two numbers are in the ratio $3 : 5$. If $9$ is subtracted from each, the new numbers are in the ratio $12 : 23$. Find the smaller number.

  1. $27$

  2. $33$

  3. $49$

  4. $55$


Correct Option: B
Explanation:

Let the numbers be $x$ and $y$

$\dfrac{x}{y}=\dfrac{3}{5}$ ...(1)

According to the question,

$\dfrac{x-9}{y-9}=\dfrac{12}{23}$ ...(2)

$x=\dfrac{3y}{5}$

$ \dfrac { \dfrac { 3y }{ 5 } -9 }{ y-9 } =\dfrac { 12 }{ 23 }  $

$  \dfrac { 3y-45 }{ 5y-45 } =\dfrac { 12 }{ 23 } $

$23(3y-45)=12(5y-45)$

$69y-1035=60y-540$

$9y=1035-540=495$

$y=55$

From (1)

$\dfrac{x}{55}=\dfrac{3}{5}$

Thus the smaller number is 33

The age of Vamsi's sister is $4\dfrac { 1 }{ 2 } $ times that of Vamsi, where as his uncle is $30$ years older than him. If the total of their ages is $56$ years, what is the age of Vamsi?

  1. $12$ years

  2. $10$ years

  3. $8$ years

  4. $4$ years


Correct Option: D
Explanation:
Let the age of Vamsi be $x$.
$\therefore$ age of Vamsi's sister  $=4 \cfrac{1}{2} \times x = \cfrac{9}{2} x$
Age of Vamsi's uncle $= 30 +$ Vamsi's age $= 30 + x$
Given that:-
age of Vamsi's sister $+$ age of Vamsi + age of Vamsi's uncle $= 56$
$\Rightarrow \; x + \cfrac{9}{2} x + 30 + x = 56$
$\Rightarrow \; \cfrac{13}{2} x = 56 - 30$
$\Rightarrow$ $13x = 52$
$\Rightarrow$ $x = 4$
Hence, age of Vamsi is $4$ years.

Deepak bought $12$ oranges for Rs $7.20$. Vimal bought x oranges more than Deepak's for Rs $9.60$. What is the value of x?

  1. $2$

  2. $5$

  3. $4$

  4. $6$


Correct Option: C
Explanation:

Deepak bought $12$ oranges for Rs.$7.20$

Thus, cost of one orange =Rs.$\dfrac{7.20}{12}$=Rs $0.60$

Vimal bought $x$ oranges more than Deepak's for Rs.$9.60$

Number of oranges Vimal bought=$\dfrac{9.60}{0.60}=16$

$x$= Number of oranges Vimal bought - Number of oranges Deepak bought

$x=16-12=4$

$x=4$

Pipes A and B can fill a tank in $18$ minutes and $12$ minutes respectively. If both the pipes are opened simultaneously, how long will they take to fill the tank?

  1. $30$ minutes

  2. $20$ minutes

  3. $10 $ minutes

  4. $7\dfrac{1}{5}$ minutes


Correct Option: D
Explanation:
Let $'V'$ be total volume of tank
Time taken by $A$ to fill tank $=18 min$
Speed of $A=\dfrac{V}{18}$
Time taken by $B$ to fill tank $=12 min$
Speed of $B=\dfrac{V}{12}$
$\therefore$  Total time taken by $A$  and  $B$  to fill tank when opened
Simultaneously $=\dfrac{V}{(\dfrac{V}{12}+\dfrac{V}{18})}$
$=\dfrac{18\times 12}{30}$
Time taken $= 7.2 min$

The sum of three non-zero prime numbers is $100$. One of them exceeds the other by $36$. Find the largest number.

  1. $73$

  2. $91$

  3. $67$

  4. $57$


Correct Option: C
Explanation:
As we know that the sum of three odd numbers cannot be even.
$\therefore$ one of the prime is even 
Since $2$ is the only prime number which is even.
$\therefore$ one of the three prime numbers is $2$.
Let one of the other prime numbers is ${p} _{1}$ then the third prime number will be ${p} _{1} + 36$. 
Now according to question,
$2 + {p} _{1} + {p} _{1} + 36 = 100$
$2{p} _{1}=62$
$p1=31$

Hence, the three prime numbers are $2, 31$ and $67$ and the largest among them is $67$.
Hence, $67$ is the correct answer.

The sum of two numbers is $45$ and their difference is $11$. What are the two numbers?

  1. $28$ and $17$

  2. $27$ and $18$

  3. $25$ and $20$

  4. $22$ and $23$


Correct Option: A
Explanation:

Let the numbers be $a$ and $b$
Given that 

$a+b=45$ ....(1)
$a-b=11$ ....(2)
Adding these two equations, we get
$2a=56$
$\Rightarrow a=28$
Substituting value of $a$ in equation (1), we get
$28+b=45$
$\Rightarrow b=45-28$
$\Rightarrow b=17$
We get $a = 28$ and $b=17$

The number of solution(s) of the equation $[x]+2{-x}=3x$, is$/$are (where $[]$ represents the greatest integer function and ${ x}$ denotes the fractional part of x$)$:

  1. $1$

  2. $2$

  3. $3$

  4. $0$


Correct Option: A
Explanation:

Given; $[x]+2\left{-x\right}=3x$

$\left{-x\right}+[-x]=-x     (\because  \left{a\right}+[a]=a)$
$\therefore  \left{-x\right}=-x-[-x]$
We know that,  $[-x]=-1-[x]$
$[x]-2x-2[-x]=3x$
$[x]-2x+2+2[x]=3x$
$3[x]=5x-2$
L.H.S is integer
$\therefore$ R.H.S must be integer
$\therefore$  $x$must be integer
As $x$ is integer , $[x]=x$
$3x=5x-2$
$x=1$
Only one solution is possible.

A number consists of two digits whose sum is 9. If 27 is added to the number, its digits are interchanged. Which of the given steps is CORRECT to find the number?
Step 1 : Let the units digit be x
Step 2 : Then, ten's digit = (9 - x)
$\therefore$  Number = 10 x (9 - x) + x
$\Rightarrow$  90 - 10x + x = (90 - 9x)
Step 3 : Adding 27 to the number 90 - 9x, we get 117 - 9x
Step 4 : Number with digits interchanged is 10x + (9 - x) = 9x + 9
Step 5 : 117 - 9x = 9x + 9
Step 6 : Therefore unit's digit = 6 and ten's digit = 3
Step 7 : Hence the number = 36.

  1. Only Step 4

  2. Both Step 1 and Step 2

  3. Step 1, 2, 3 and 4

  4. All steps are correct


Correct Option: D
Explanation:

In given question we have to find the number.

$\Rightarrow$  To find the numbers $7$ steps are given.
$\Rightarrow$  All $7$ steps are correct to find the required  number.
$\therefore$   Correct answer is option $D.$

Peter's age in $10$ years will be $12$ less than $4$ times his current age. What is Peter's current age (in years)?

  1. $7.33$

  2. $7.71$

  3. $6.04$

  4. $6.49$


Correct Option: A
Explanation:

Let Peter's current age be $x$ years

According to question,

$\Rightarrow$$(x+10)=4x-12$

$\Rightarrow$$4x-(x+10)=12$

$\Rightarrow$$4x-x-10=12$

$\Rightarrow$ $3x=22$


$\Rightarrow$$x=\cfrac { 22 }{ 3 } =7.33$


Peter's age $=7.33$ years

Arvind has Piggybank. It is full of one-rupee and fifty paise coins. It contains $3$ times as many fifty paise coins as one rupee coins. The total amount of money in the bank is $Rs\ 35$. How many one-rupee and fifty paise coins are there in the bank ?(respectively)

  1. $14,\ 42$

  2. $15,\ 42$

  3. $14,\ 52$

  4. None of these


Correct Option: A
Explanation:

Let no. of fifty paise coins be $x$ and no.of one Rupees coins be $y$

then $x=3y$

According to question 
$0.50 \times x+1 \times y=35\$
$\Rightarrow 0.5x+y=35\$
$\Rightarrow 0.5 \times 3y+y=35\$
$1.5y+y=35\$
$\Rightarrow 2.5y=35\$
$\Rightarrow y=\dfrac{350}{25}\$
$\Rightarrow y=14\$
So,
    $x=3y\$
$=3 \times 14\$
$=42$

Therefore no.of fifty paise coins is $42$ ans no.of one Ruppee coin is $14$.

Sum of the ages of three friends $x$ years ago was $y$ years. Then what will be the sum of their ages now?

  1. $3x+y$

  2. $x+3y$

  3. $3x-y$

  4. $x-3y$


Correct Option: A
Explanation:

Let their present age be $a,b,c$


Sum of their present age $=a+b+c$

Their ages $x$ years ago $a-x,b-x,c-x$

Sum $=a+b+c-3x$

Given $a+b+c-3x=y$

$a+b+c=y+3x=3x+y$


So option $A$ is correct.

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