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Odd and even numbers - class-VI

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If the number of consecutive odd integers whose sum can be expressed as $50^2 - 13^2$ is k then k, can be 

  1. 33

  2. 35

  3. 37

  4. 39


Correct Option: C
Explanation:

Sum of odd $n$ consecutive numbers $n^2$

$\therefore (1+3+5\dots\dots (2n-1))=n^2$
where $n$ represents the number of terms.
$\therefore 50^2=1+3+5\dots 99=50\text{ }terms$
$\therefore 13^2=1+3+5\dots 25=13\text{ }terms$
$\therefore 50^2-13^2$$=(1+3+5\dots 99)-(1+3+5\dots 25)\=(27+29\dots 99)\ =37\text{ }terms.$

Let A, B, C, D, E be the smallest positive integers having 10, 12, 15, 16, 20 positive divisors respectively. Then
A+B

  1. 108

  2. 110

  3. 126

  4. 120


Correct Option: A

Mark the correct alternative of the following.
The successor of the smallest prime number is?

  1. $1$

  2. $2$

  3. $3$

  4. $4$


Correct Option: C
Explanation:

The smallest prime number is $2$.

Hence the successor of $2$ is $3$.
So the successor of the smallest prime number is $3$.

The general form of an even number is 

  1. $2n-1$

  2. $2n$

  3. $2n+1$

  4. $2$


Correct Option: B
Explanation:

An even number is a number which has a factor of $2$.

Therefore, general term will be $2n$

Odd numbers are not divisible by

  1. one

  2. two

  3. odd numbers

  4. negative integers


Correct Option: B
Explanation:

Odd numbers are not divisible by $2$

Difference between two even numbers after and before $2n$, where $n$ is a positive number, is-

  1. $0$

  2. $4$

  3. $2$

  4. $6$


Correct Option: B
Explanation:
Even number after $2n=2n+2$
Even number before $2n=2n-2$
Difference$=2n+2-\left(2n-2\right)=4$

Pick out even number:
$123, 246, 145, 279$

  1. $123$

  2. $ 246$

  3. $ 145$

  4. $279$


Correct Option: B
Explanation:

A number is even if the digit in One's place is divisible by $2$.


Out of the numbers $123,246,145,279$ only $246$ is even as it has $6$ at unit's place which is divisible by $2$.

The sum of even numbers between $1$ and $31$ is:

  1. $6$

  2. $28$

  3. $240$

  4. $512$


Correct Option: C
Explanation:

Let ${S} _{n}=(2+4+6+.....+30)$. This is an A.P in which $a=2,d=2$ and $l=30$
Let the number of terms be $n$. Then,
$a+(n-1)d=30$
$\Rightarrow$ $2+(n-1)\times 2=30$
$\Rightarrow$ $n=15$
$\therefore$ ${S} _{n}=\cfrac{n}{2}(a+l)=\cfrac{15}{2}\times (2+30)=(15\times 16)=240$.

$-1$ is an odd integer, 5th consecutive integer is

  1. Odd

  2. Even

  3. Zero

  4. None


Correct Option: B
Explanation:

$-5,-4,-3,-2,-1,0,1,2,3,4,5$

This is set of integers in neighbourhood of $-1$ as per number line.
$5$th conescutive integer as seen from above, is $4$ which is Even.

Which one of the following is even?

  1. $9 \times 14$

  2. $15 \times 17$

  3. $17 \times 9 $

  4. $11 \times 19$


Correct Option: A
Explanation:

$9\times 14=9\times 2\times 7$

$\Rightarrow 9\times 14$ has $2$ as one of its factor.
So it is an even number
None of the other options has $2$ as their multiple
So option $A$ is correct.

Which of the following is positive even integer?

  1. $4$

  2. $-4$

  3. $0.3$

  4. $-2$


Correct Option: A
Explanation:

Out of the following the integer which is positive and even is 4. Thus, option A is correct.

Every even integer can be written as  
(Note:  $m$ is any integer)

  1. $m$

  2. $m + 1$

  3. $2m$

  4. $2m + 1$


Correct Option: C
Explanation:

Any even integer is divisible by $2$.

so we can write it as  $2m$

If you add two even numbers together, the answer is

  1. 0

  2. Always even

  3. Sometimes even

  4. Sometimes odd


Correct Option: B
Explanation:

If we add two even numbers the answer is always even.

Let $2a$ and $2b$ be two even numbers as both are divisible by $2$
Sum $=2a+2b$
Sum $=2(a+b)$
which is also divisible by $2$ . So the sum is even.
So option $B$ is correct.

If m, n, o, p and q are integers then $m(n + o) (p - q)$ must be even then which of the following is even?

  1. $m + n$

  2. $n + p$

  3. m

  4. p


Correct Option: C
Explanation:

$ Given\quad that\quad m,n,o,p\quad and\quad q\quad are\quad integers.\ \therefore \quad (n+o)\quad is\quad an\quad integer\ \quad \quad (p-q)\quad is\quad an\quad integer\ \therefore \quad m(n+o)(p-q)\quad is\quad a\quad product\quad of\quad 3\quad integers.\ The\quad product\quad to\quad be\quad even\quad one\quad of\quad the\quad factors\quad to\quad be\quad even.\ either\quad m\quad be\quad even\longrightarrow option\quad C\ or\quad (n+o)\quad be\quad even\longrightarrow no\quad option\ or\quad (p-q)\quad be\quad even\longrightarrow no\quad option.\ \therefore \quad option\quad C\quad is\quad the\quad answer. $

State whether following statement is true or false. 
Sum of two odd numbers is always an odd number.

  1. True

  2. False


Correct Option: B
Explanation:
$1+3=4\\7+9=16$
Sum of $2$ odd nos. is even

Pick odd ineger:
$3, -4, -3, 5$

  1. $-4, 5$

  2. $-4,-3$

  3. $3, -3, 5$

  4. $-4$


Correct Option: C
Explanation:
An odd number is an integer which is not divisible by two. If it is divided by two, then the result is a fraction. The set of odd integers is $-5,-3,-1,1,3,5,7,.....$

Hence, the odd integers are $3,-3,5$, whereas $-4$ is not an odd integer because it is divisible by $2$.

If you add two odd numbers together, the answer is

  1. Always Even

  2. Always Odd

  3. Sometimes Even

  4. 1


Correct Option: A
Explanation:

If we add two odd numbers the sum is always even.

Let $2n-1$ and $2m-1$ be two odd numbers. 
Sum $=2n-1+2m-1$
Sum $=2n+2m-2$
Sum $=2(n+m-1)$
which is divisible by $2$ . So the sum is even.
Option $A$ is correct.

Write two odd integers lesser than $1$.

  1. $1,3$

  2. $-1,-3$

  3. $-3,5$

  4. $0,1$


Correct Option: B
Explanation:
An odd number is an integer which is not divisible by two. If it is divided by two, then the result is a fraction. The set of odd integers is $-5,-3,-1,1,3,5,7,.....$

The following set of integers is lesser than $1$:

$.....-5,-3,-1,1$

Hence, two of the odd integers lesser than $1$ are $-1,-3$.

If k is a positive integer, then $k(k+1)(k+3)$ is

  1. even only when k is even

  2. even only when k is odd

  3. Always odd

  4. Always even


Correct Option: D
Explanation:

Suppose $k$ is even

Then $k(k+1)(k+3)$ is even as $k$ will be divisible by $2$
Now if $k$ is odd.
Then $(k+1)$ and $(k+3)$ are even
$\Rightarrow k(k+1)(k+3)$ is also even.
So $k(k+1)(k+3)$ is always even.
So option $D$ is correct.

Write $2$ even integers greater than  $-4$

  1. $-2,-6$

  2. $-6,-8$

  3. $6,8$

  4. $-3,2$


Correct Option: C
Explanation:
An even number is an integer which is "evenly divisible" by two. This means that if the integer is divided by $2$, it yields no remainder. The set of even integers is $-6,-4,-2,2,4,6,8,.....$

The following set of integers is greater than $-4$:

$-2,2,4,6,8,.....$

Hence, two of the even integers greater than $-4$ are $6,8$.

Example of an even number from the following is:

  1. $10351$

  2. $20989$

  3. $69007$

  4. $973572$


Correct Option: D
Explanation:

The number which ends with $2,4,6,8,0$ are divisible by $2$.

So, only $973572$ is divisible by $2$.
Hence, the answer is $973572$.

The numbers which are not multiples of $2$ are called _______.

  1. even

  2. odd

  3. prime

  4. composite


Correct Option: B
Explanation:

The numbers $1,3,5,7,9$ etc are called odd number which is not divisible by $2$ and any number which ends which these numbers are also called odd number. 

So, the numbers which are not multiples of $2$ are called odd.
Hence, the answer is odd.

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