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Vedic methods of multiplication - class-IX

Description: vedic methods of multiplication
Number of Questions: 32
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A jar can hold $4250\,ml$ honey. How much $litre$ honey will be needed to fill $4$ jars?

  1. $16$

  2. $15$

  3. $17$

  4. $17000$


Correct Option: C
Explanation:
A jar can hold$=4000+250$
$=4250㎖$ honey
Total honey needed to fill
$4$ jars$=4250\times 4$
$=17000㎖$
$=17ℓ$ is the correct answer.

Monika takes $\displaystyle{\dfrac{1}{6}}$ hour to walk to the playground and $\displaystyle{\dfrac{1}{3}}$ hour to walk from the playground to school. How much time does it take her to walk to the playground and then to school ? 

  1. $\displaystyle{\dfrac{2}{9}}$ hour

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

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

  4. $\displaystyle{\dfrac{2}{3}}$ hour


Correct Option: C
Explanation:

Monika takes $\dfrac{1}{6}$ hour to walk to the playground.

And $\dfrac{1}{3}$ hour to walk from the playground to school.

She will take time to walk to the playground and then to school
$=\dfrac{1}{6}+\dfrac{1}{3}$
$=\dfrac{1+2}{6}$
$=\dfrac{1}{2}$ hour

Hence, this is the answer.

In Vedic period, squares and circular shaped altars were used for household rituals, while altars whose shapes were combination of rectangles, triangles and trapeziums were used for public worship.

  1. True

  2. False

  3. Ambiguous

  4. Data Insufficient


Correct Option: A
Explanation:

In ancient India, squares and circular altars were used for household rituals.

The geometry of the Vedic period originated with the construction of altars (or vedis) and fireplaces for performing Vedic rites. Square and circular altars were used for household rituals, while altars, whose shapes were combinations of rectangles, triangles and trapeziums, were required for public worship.

Half of a number is 12. What is $\dfrac{3}{4}$ of the same number ?

  1. 24

  2. 36

  3. 9

  4. 18


Correct Option: D
Explanation:

Let the number be $x$.

 

Since,

$ \dfrac{x}{2}=12 $

$ x=24 $

 

Since,

$ \Rightarrow \dfrac{3}{4}\times 24 $

$ \Rightarrow 18 $

 

Hence, this is the answer.

Sonia talked on the telephone to two friends. She talked to Shivani for $\displaystyle{\dfrac{1}{4}}$ hour to Geetika for $\displaystyle{\dfrac{1}{3}}$ How much time did Sonia spend on the telephone ?

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

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

  3. $\displaystyle{\dfrac{5}{12}}$

  4. $\displaystyle{\dfrac{7}{12}}$


Correct Option: D
Explanation:

Sonia talked to Shivani for $=\dfrac{1}{4}$ hour

Sonia talked to Geetika for $=\dfrac{1}{3}$ hour

She spend time on the telephone will be
$=\dfrac{1}{4}+\dfrac{1}{3}$
$=\dfrac{7}{12}$ hour

Hence, this is the answer.

Victor can throw a ball 50$\displaystyle{\dfrac{3}{5}}$ feet. Parth can throw the same ball 48$\displaystyle{\dfrac{1}{3}}$ feet. How much farther can Victor throw the ball than Parth ? 

  1. 2$\displaystyle{\dfrac{2}{15}}$ feet

  2. 2$\displaystyle{\dfrac{4}{15}}$ feet

  3. 2$\displaystyle{\dfrac{3}{5}}$ feet

  4. 2$\displaystyle{\dfrac{4}{5}}$ feet


Correct Option: B
Explanation:

Victor can throw a ball $=50\dfrac{3}{5}$ feet

Parth can throw the same ball $=48\dfrac{1}{5}$ feet

Difference,
$=50\dfrac{3}{5}-48\dfrac{1}{3}$
$=\dfrac{253}{5}-\dfrac{145}{3}$
$=\dfrac{253}{5}-\dfrac{145}{3}$
$=\dfrac{34}{15}$
$=2\dfrac{4}{15}$ feet

Hence, this is the answer.

Using vedic mathematics term "Ekadhik", find the value of $135^2$.

  1. $18625$

  2. $18325$

  3. $19425$

  4. $18225$


Correct Option: D

Using vedic mathematics term "Ekadhik", find the value of $35^2$.

  1. $11025$

  2. $1325$

  3. $1225$

  4. None of these


Correct Option: C

Using vedic mathematics term "Ekadhik", find the value of $65^2$.

  1. $4225$

  2. $5325$

  3. $4325$

  4. $4645$


Correct Option: A

If $60$% of $\cfrac{3}{5}$ of a number is $36$, then the number is:

  1. $80$

  2. $100$

  3. $75$

  4. $90$


Correct Option: B
Explanation:

Let the number be $x$. Then
$60$% of $\cfrac{3}{5}$ of $x=36$
$\Rightarrow$ $\cfrac{60}{100}\times \cfrac{3}{5}\times x=36$
$\Rightarrow$ $x=(36\times \cfrac{25}{9})=100$
$\therefore$ Required number $=100$

Identify the larger fraction between $\dfrac{4}{5}, \dfrac{5}{9}$ using Vedic mathematics.

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

  2. $\dfrac{5}{9}$

  3. Both are equal

  4. None of these


Correct Option: A
Explanation:

5/4 , 5/9
Difference of cross product = 45 - 20 = 25
If the difference of the cross product is positive then the first fraction is larger.
hence 5/4 is larger.

Find Ekadhikena Purvena of the number $37$.

  1. $38$

  2. $36$

  3. $30$

  4. None of these


Correct Option: A
Explanation:

'Ekadhikena Purvena'   means  “by one more than the previous”
So, Ekadhikena Purvena of the number 37 is 38.

Find Ekanyunena Purvena of the number $37$.

  1. $35$

  2. $30$

  3. $36$

  4. None of these


Correct Option: C
Explanation:

'Ekanyunena Purvena'   means  “by one less than the previous”
So, Ekadhikena Purvena of the number 37 is 37 - 1 = 36.

Identify the larger fraction between $\dfrac{2}{3}, \dfrac{5}{8}$ using Vedic mathematics.

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

  2. $\dfrac{5}{8}$

  3. Both are equal

  4. None of these


Correct Option: A
Explanation:

2/3, 5/8
Difference of cross product = 16 - 15 = 1

If the difference of the cross product is positive then the first fraction is larger.
So, 2/3 is larger fraction.

Identify the larger fraction between $\dfrac{7}{12}, \dfrac{9}{20}$ using Vedic mathematics.

  1. $\dfrac{7}{12}$

  2. $\dfrac{9}{20}$

  3. Both are equal

  4. None of these


Correct Option: A
Explanation:

7/12, 9/20

Difference of cross product = 140 - 108 = 32

If the difference of the cross product is positive then the first fraction is larger.
So, 7/12 is larger fraction.

Find Ekadhikena Purvena of the number $200$.

  1. $201$

  2. $199$

  3. $200$

  4. None of these


Correct Option: A
Explanation:

'Ekadhikena Purvena'   means  “by one more than the previous”
So, Ekadhikena Purvena of the number 200 is 201.

Find Ekadhikena Purvena of the number $99$.

  1. $101$

  2. $90$

  3. $95$

  4. None of these


Correct Option: D
Explanation:

'Ekadhikena Purvena'   means  “by one more than the previous”
So, Ekadhikena Purvena of the number 99 is 100.

Find Ekanyunena Purvena of the number $99$.

  1. $100$

  2. $98$

  3. $101$

  4. None of these


Correct Option: B
Explanation:

'Ekanyunena Purvena'   means  “by one less than the previous”
So, Ekadhikena Purvena of the number 99 is 99 - 1 = 98.

Find the correct representation of Ekadhikena Purvena of the number $199$.

  1. $199-1$

  2. $199+1$

  3. $199/100$

  4. None of these


Correct Option: B
Explanation:

'Ekadhikena Purvena'   means  “by one more than the previous”
So, Ekadhikena Purvena of the number 199 is 199 + 1 = 200.

Identify the larger fraction between $\dfrac{11}{21}, \dfrac{12}{25}$ using Vedic mathematics.

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

  2. $\dfrac{12}{25}$

  3. Both are equal

  4. None of these


Correct Option: A
Explanation:

11/21, 12/25
Difference of cross product = 275 - 252 = 23

If the difference of the cross product is positive then the first fraction is larger.
So, 11/21 is larger fraction.

$\displaystyle\frac{1}{5}$ of $\displaystyle\frac{2}{7}$ of $\displaystyle \frac{8}{3}$ of $4095=?$

  1. $642$

  2. $598$

  3. $648$

  4. $475$

  5. None of these


Correct Option: E
Explanation:

$\displaystyle \frac{1}{5}$ of $\displaystyle\frac{2}{7}$ of $\displaystyle\frac{8}{3}$ of $4095$
$=\displaystyle\frac{1}{5}\times \frac{2}{7}\times \frac{8}{3}\times 4095=624$.

Hence the correct answer is option E

The value of $3\dfrac{1}{12}$ - $\big[ 1\dfrac{3}{4} $+$\big[$ 2$\dfrac{1}{2}$ - $\big(1\dfrac{1}{2}$ - $\dfrac{1}{3}$ $\big)\big]\big]$

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

  2. $2$

  3. $1$

  4. $0$


Correct Option: D
Explanation:

We have, 3$\dfrac{1}{12}$ - $\bigg[$ 1$\dfrac{3}{4}$ +$\big[2\dfrac{1}{2}$ - $\big(1\dfrac{1}{2}$ - $\dfrac{1}{3}\big)\big]\bigg]$
= $\dfrac{37}{12}$ - $\bigg[$ $ \dfrac{7}{4}$ +$\big[\dfrac{5}{2}$ - $\big(\dfrac{3}{2}$ - $\dfrac{1}{3}$ $\big)\big]\bigg]$
= $\dfrac{37}{12}$ - $\bigg[\dfrac{7}{4}$ + $\big[\dfrac{5}{2}$ - $\big(\dfrac{9-2}{6}\big)\big]\bigg]$   $\bigg[ \because$ LCM of 2,3 =6$\bigg]$
= $\dfrac{37}{12}$ - $\big[\dfrac{7}{4}$ + $\big(\dfrac{5}{2}$ - $\dfrac{7}{6}\big)\big]$
=$\dfrac{37}{12}$ - $\big(\dfrac{7}{4}$ + $\big(\dfrac{15-7}{6}\big)\big]$        $\bigg[\because$ LCM of 2, 6 = 6$\bigg]$
=$\dfrac{37}{12}$ - $\big[\dfrac{7}{4}$ + $\dfrac{8}{6}$ $\big]$
= $\dfrac{37}{12}$ - $\big[\dfrac{21+16}{12}$ $\big]$            $\big[\because$ LCM of 4, 6 = 12 $\big]$
= $\dfrac{37}{12}$ - $\dfrac{37}{12}$ = 0

Trishika bought some strawberries. $\cfrac{1}{8}$ of the strawberries were rotten and had to be thrown away. Trishika then used $25$ strawberries to bake a cake. She then had $\cfrac{1}{4}$ of the total strawberries left.
(a) How many strawberries did she have at first?
(b) If Trishika shared the remaining strawberries between her two sons equally, what fraction of the strawberries did each of them receive?

  1. $(a) 70; (b) \dfrac{1}{8}$

  2. $(a) 50; (b) \dfrac{4}{8}$

  3. $(a) 40; (b) \dfrac{1}{8}$

  4. $(a) 40; (b) \dfrac{1}{4}$


Correct Option: C
Explanation:
Let, the total no of strawberries Trishika had $x$
No of rotten strawberries $=$ $\dfrac{1}{8}x$
No of strawberries used to bake a cake$=$25
$\therefore$ No of strawberries left$=$$x-(\dfrac{1}{8}x+25)$
A.T.Q,
$x-\dfrac{1}{8}x-25$=$\dfrac{1}{4}x$
$\implies x-\dfrac{1}{8}x-\dfrac{1}{4}x$=$25$
$\implies \dfrac{8x-x-2x}{8}$=$25$
$\implies \dfrac{5x}{8}$=$25$
$ \implies x$=$40$
b)  No of remaining strawberries $=$ $\dfrac{1}{4}x$
Shared among two sons equally$=$$\dfrac{1}{4}x \div 2$
Share of strawberries recieveed by each son$=$$\dfrac{1}{8}x$

$\cfrac{1}{10}$ of a rod is coloured red, $\cfrac{1}{20}$ orange, $\cfrac{1}{30}$ yellow, $\cfrac{1}{40}$ green, $\cfrac{1}{50}$ blue, $\cfrac{1}{60}$ black and the rest violet. If the length of the violet portion is $12.06m$, then what is the length of the rod?

  1. $16m$

  2. $18m$

  3. $20m$

  4. $30m$


Correct Option: A
Explanation:

Let the length of the rod be $x$ $m$
$\therefore$ Length of the rod coloured be red$=\cfrac{1}{10}$ $x$ $m$
$\therefore$ Length of the rod coloured be orange$=\cfrac{1}{20}$ $x$ $m$
Length of the rod coloured be yellow$=\cfrac{1}{30}$ $x$ $m$
Length of the rod coloured be green$=\cfrac{1}{40}$ $x$ $m$
Length of the rod coloured be blue$=\cfrac{1}{50}$ $x$ $m$
Length of the rod coloured be black$=\cfrac{1}{60}$ $x$ $m$
Length of the rod coloured be violet$=12.08m$
$\therefore$ According to question
$\cfrac { 1 }{ 10 } x+\cfrac { 1 }{ 20 } x+\cfrac { 1 }{ 30 } x+\cfrac { 1 }{ 40 } x+\cfrac { 1 }{ 50 } x+12.08=x$
$\Rightarrow x-\cfrac { 49 }{ 200 } x=12.08\Rightarrow \cfrac { 151 }{ 200 } x=12.08\Rightarrow x=16$
$\therefore$ Length of the rod $=16m$

If $'+'$ means $'\times', '-'$ means $'\div', '\times'$ means $'-'$ and $'\div'$ means $'+'$, then $2 + 15 \div 15 - 3 \times 8$ is equal to

  1. $43$

  2. $27$

  3. $35$

  4. $28$


Correct Option: B
Explanation:

After interchanging the signs,
$2\times 15 + 15\div 3 - 8 = ?$
$\Rightarrow 2\times 15 + 5 - 8 = ?\Rightarrow 30 + 5 - 8 =?$
$? = 35 - 8 = 27$.

Which of the following fraction equals $\displaystyle101\frac{3}{5}\%$

  1. $\displaystyle\frac{508}{5}$

  2. $\displaystyle\frac{254}{5}$

  3. $\displaystyle\frac{51}{25}$

  4. $\displaystyle\frac{127}{125}$


Correct Option: A
Explanation:

$ 101 \dfrac {3}{5} = \dfrac {101 \times 5 + 3}{5} = \dfrac {505+3}{5} = \dfrac {508}{5}$

Two candles are of different lengths and thickness. The short and the long ones can burn respectively for $3.5$ hour and $5$ hour. After burning for 2 hour, the lengths of the candles become equal in length. What fraction of the long candle's height was the short candle initially ?

  1. $\displaystyle\frac{2}{7}$

  2. $\displaystyle\frac{5}{7}$

  3. $\displaystyle\frac{3}{5}$

  4. $\displaystyle\frac{4}{5}$


Correct Option: B
Explanation:

Shorter candle ray ${L} _{1}$ burns in 3.5 hours.
So in 2 hours $\displaystyle\frac{{L} _{1}}{3.5} \times 2$ of the candle will burn
Remaining length $= {L} _{1} - \displaystyle\frac{2{L} _{1}}{3.5} = \displaystyle\frac{1.5}{3.5}{L} _{1}$
The longer candle, ${L} _{2}$ burns in 5 hours. So in 2 hours $\displaystyle\frac{{L} _{2}}{5} \times 2$ will burn
Remaining length $= {L} _{2} - \displaystyle\frac{2{L} _{2}}{5} = \displaystyle\frac{3}{5} {L} _{2}$
Equating $\displaystyle\frac{1.5}{3.5} {L} _{1} = \displaystyle\frac{3}{5}{L} _{2}$
$\Rightarrow   \displaystyle\frac{{L} _{1}}{{L} _{2}} = \displaystyle\frac{3}{5} \times \displaystyle\frac{3.5}{1.5} = \displaystyle\frac{7}{5}$
Note : There is a mistake in question. It should read the short and the long ones can burn respectively for 5 hours and 3.56 hours. The answer $\left(\displaystyle\frac{{L} _{1}}{{L} _{2}}\right)$ will come out to be $\displaystyle\frac{5}{7}$ in that case.

Fraction  $\displaystyle \frac { 2 }{ 5 }, \frac {3} {10} , \frac {9} {10}, \frac {16} {35} $ in ascending order are:

  1. $\displaystyle \frac { 2 }{ 5 }, \frac {3} {10} , \frac {9} {10}, \frac {16} {35} $

  2. $\displaystyle \frac { 3 }{ 10 }, \frac {2} {5}, \frac {16} {35}, \frac {9} {14} $

  3. $\displaystyle \frac { 3 }{ 10 } , \frac {9} {14} , \frac {16} {35}, \frac {2} {5} $

  4. $\displaystyle \frac { 16 }{ 35 } , \frac {2} {5} , \frac {3} {10}, \frac {9} {14} $


Correct Option: B
Explanation:

The given Fraction are $\displaystyle \frac { 2 }{ 5 }, \frac {3} {10} , \frac {9} {10}, \frac {16} {35} $
LCM of 5, 10, 14, 35 = $\displaystyle (5\times 2\times 7\times)= 70 $
Now change each of the following into an equivalent fraction having 70 as its denominator.
Now, $\displaystyle \frac { 2 }{ 5 } =\frac { 2\times 14 }{ 5\times 14 } =\frac { 28 }{ 70 } \ \frac { 3 }{ 10 } =\frac { 3\times 7 }{ 10\times 7 } =\frac { 21 }{ 70 } \ \frac { 9 }{ 14 } =\frac { 9\times 5 }{ 14\times 5 } =\frac { 45 }{ 70 } \ and\quad \frac { 16 }{ 35 } =\frac { 16\times 2 }{ 35\times 2 } =\frac { 32 }{ 70 } \ Clearly,\quad \frac { 28 }{ 70 } >\frac { 21 }{ 70 } <\frac { 45 }{ 70 } >\frac { 32 }{ 70 } \ Hence,\quad \frac { 3 }{ 10 } <\frac { 2 }{ 5 } <\frac { 16 }{ 35 } <\frac { 9 }{ 14 } $

The value of the expression $\dfrac { 1 }{ \sqrt { 11-2\sqrt { 30 }  }  } -\dfrac { 3 }{ \sqrt { 7-2\sqrt { 10 }  }  } -\dfrac { 4 }{ \sqrt { 8+4\sqrt { 3 }  }  } $ after simplification is

  1. $\sqrt { 30 } $

  2. $2\sqrt { 10 } $

  3. $1$

  4. $0$


Correct Option: D
Explanation:

$\dfrac { 1 }{ \sqrt { 11-2\sqrt { 30 }  }  } -\dfrac { 3 }{ \sqrt { 7-2\sqrt { 10 }  }  } -\dfrac { 4 }{ \sqrt { 8+4\sqrt { 3 }  }  } $


$=\left (\dfrac { 1 }{ { 11-2\sqrt { 30 }  }  }\right)^{\frac{1}{2}} -\left( \dfrac { 3 }{ { 7-2\sqrt { 10 }  }  }\right)^{\frac{1}{2}} -\left( \dfrac { 4 }{ { 8+4\sqrt { 3 }  }  }\right)^{\frac{1}{2}} $


$=\left (\dfrac { 1 }{ { 5+6-2\sqrt {5}\sqrt{6}}}\right)^{\frac{1}{2}} -\left( \dfrac { 3 }{ { 5+2-2\sqrt {5}\sqrt{2}}}\right)^{\frac{1}{2}} -\left( \dfrac { 4 }{ {6+2+2\sqrt {6}\sqrt{2}  }  }\right)^{\frac{1}{2}} $

$={ \left( \dfrac { 1 }{ (\sqrt { 6 } -\sqrt { 5 } )^2 }  \right)  }^{ \frac { 1 }{ 2 }  }-3{ \left( \dfrac { 1 }{( \sqrt { 5 } -\sqrt { 2 } )^2 }  \right)  }^{ \frac { 1 }{ 2 }  }-4{ \left( \dfrac { 1 }{ (\sqrt { 6 } +\sqrt { 2 } )^2 }  \right)  }^{ \frac { 1 }{ 2 }  }$

$={ \left( \dfrac { 1 }{ \sqrt { 6 } -\sqrt { 5 }  }  \right)  }^{ \frac { 2 }{ 2 }  }-3{ \left( \dfrac { 1 }{ \sqrt { 5 } -\sqrt { 2 }  }  \right)  }^{ \frac { 2 }{ 2 }  }-4{ \left( \dfrac { 1 }{ \sqrt { 6 } +\sqrt { 2 }  }  \right)  }^{ \frac { 2 }{ 2 }  }$

$={ \left( \dfrac { 1 }{ \sqrt { 6 } -\sqrt { 5 }  } \times {\dfrac{\sqrt{6}+\sqrt{5}}{\sqrt{6}+\sqrt{5}}} \right)  }^{ \frac { 2 }{ 2 }  }-3{ \left( \dfrac { 1 }{ \sqrt { 5 } -\sqrt { 2 }  } \times{\dfrac{\sqrt{5}+\sqrt{2}}{\sqrt{5}+\sqrt{2}}} \right)  }^{ \frac { 2 }{ 2 }  }-4{ \left( \dfrac { 1 }{ \sqrt { 6 } +\sqrt { 2 }  } \times{\dfrac{\sqrt{6}-\sqrt{2}}{\sqrt{6}-\sqrt{2}}} \right)  }^{ \frac { 2 }{ 2 }  }$

$=\left( \sqrt { 6 } +\sqrt { 5 }  \right) -\left( \sqrt { 5 } +\sqrt { 2 }  \right) -\left( \sqrt { 6 } -\sqrt { 2 }  \right) =0$
Hence, option D is correct.

Which of the following statement is CORRECT?
Statement-1: Mrs. Soni bought 7$\dfrac{1}{2}$ litres of milk. Out of this, 5$\dfrac{3}{4}$ liters was consumed. 1$\dfrac{1}{3}$ liters of milk is left with her.
Statement-2: Amit reads $\dfrac{3}{5}$ of a book. He finds that there are still 80 pages left to be read. The total number of pages in the book is $200.$

  1. Only statement-1

  2. Only Statement-2

  3. Both Statement-1 and Statement-2

  4. Neither Statement-1 nor Statement-2


Correct Option: B
Explanation:

Statement-1: Total quantity of milk bought = 7$\dfrac{1}{2}$litres = $\dfrac{15}{2}$litres
Quantity of milk consumed = 5$\dfrac{3}{4}$litres
                                            = $\dfrac{23}{4}$ litres
$\therefore$ Quantity of milk left = $\big(\dfrac{15}{2}$ - $\dfrac{23}{4}$$\big)$ litres
= $\big(\dfrac{30-23}{4}\big)$ litres = $\dfrac{7}{4}$ = 1$\dfrac{3}{4}$ litres
Statement-2: Let total number of pages in the book be x.
According to question,
$\dfrac{3}{5}$x + 80 = x
$\Rightarrow$ x - $\dfrac{3}{5}$x = 80 $\Rightarrow$ x = $\dfrac{80\times5}{2}$
$\Rightarrow$ x = 200
$\therefore$ Total number of pages = 200
Hence, only statements-2 is true.

Two pipes $A$ and $B$ can fill a cistern in $37\dfrac {1}{2}$ minutes and $45$ minutes respectively. Both pipes are opened, the cistern will be filled just in half an hour, if the pipe $B$ is turned off after.

  1. $15\ minutes$

  2. $10\ minutes$

  3. $5\ minutes$

  4. $9\ minutes$


Correct Option: D
Explanation:

Let the capacity of cistern be $225$ units $\left (LCM\ of \dfrac {75}{2}\ and\ 45\right )$
$A$ does $= \dfrac {225}{75}\times 2 = 6\ units/ min$
$B$ does $= \dfrac {225}{45} = 5\ units/ min$.
Let pipe is turned off after $x$ minutes.
According to the question,
$6\times 30 + 5\times x = 225$
$5x = 225 - 180 = 45$
$x = 9$
After $9$ minutes, pipe $B$ is turned off.

Two trains starts from stations $A$ and $B$ and travel towards each other at speed of $50\ km/hr$ and $60\ km/hr$ respectively. At the time of their meeting, the second train has travelled $120\ km$ more than the first. The distance between $A$ and $B$ is

  1. $990\ km$

  2. $1200\ km$

  3. $1320\ km$

  4. $1440\ km$


Correct Option: C
Explanation:

Speed of train $A = 50\ kmph$
Speed of train $B = 60\ kmph$
Since, time is constant
$Speed \propto$ Distance covered
$\dfrac {S _{A}}{S _{B}} = \dfrac {D _{A}}{D _{B}}$
$\dfrac {50}{60} = \dfrac {D _{A}}{D _{B}}\Rightarrow \dfrac {5}{6} = \dfrac {D _{A}}{D _{B}}$
Given that train $B$ has travelled $120\ km$ extra.
$6x - 5x = 120$
$x = 120$
The distance between $A$ and $B = 6x + 5x = 11x$
$= 11\times 120 = 1320$
Alternate Method:
Let train $A$ start form station $A$ and $B$ from station $B$.
Let the trains $A$ and $B$ meet after/ hours.
$\therefore$ Distance covered by train $A$ in $t$ hours $= 50t$
Distance covered by train $B$ in $t$ hours $= 60t\ km$.
According to the question,
$60t - 50t = 120$
$\Rightarrow t = \dfrac {120}{10} = 12\ hours$.
$\therefore$ Distance $AB = 50\times 12 + 60 \times 12$
$= 600 + 720 = 1320\ km$.

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