Tag: mental additions and subtractions

Questions Related to mental additions and subtractions

What will we get if we subtract $1$ from smallest $6$-digit number?

maths operations adding and subtracting numbers using place value addition & subtraction mental additions and subtractions

  1. $99999$

  2. $100009$

  3. $19999$

  4. $999999$

Show answer
Correct Option: A
Explanation:

The smallest 6 digit number $=1,00,000$

therefore,
$100000-1=99999$

Raghu is $21$ years old and Kavita is $72$ years old. The sum of their ages is

maths operations adding and subtracting numbers using place value addition & subtraction mental additions and subtractions

  1. $83$

  2. $85$

  3. $93$

  4. $103$

Show answer
Correct Option: C
Explanation:

Age of Raghu $= 21 $ years
Age of Kavita $= 72$ years
Therefore, sum of their ages $= 21+72 =93 $ years

The sum of the digit of a two digit number is $15$ and the difference between the digits is $3$. What the two digit number?

maths operations adding and subtracting numbers using place value addition & subtraction mental additions and subtractions

  1. $69$

  2. $78$

  3. $90$

  4. $86$

Show answer
Correct Option: A
Explanation:

Sum of digit of $2$ digit number $10x+y$ is $15$

$x+y=15$
is $3, x-y=3\x+y=15\x-y=3\----\2x=18\x=9$
So, $y=15-x\15-9\y=6$
solution can be $96$ or $69$
Answer $A$

Neha, Joy and Karan are helping Uncle Shyam in picking apples. Uncle Shyam gives each of them $230$ apples. How many apples do Neha, Joy and Karan have in all? 

maths operations adding and subtracting numbers using place value addition & subtraction mental additions and subtractions

  1. $580$

  2. $690$

  3. $740$

  4. $870$

Show answer
Correct Option: B
Explanation:

$\Rightarrow$  Uncle shyam gives $230$ each apples to Neha, Joy and Karan.

$\Rightarrow$  Total apples Neha, Joy and Karan have in all$=230+230+230=690\,apples.$

If $a+b=30$ and $ab=176$, find $a^{3}+b^{3}$

maths operations adding and subtracting numbers using place value addition & subtraction mental additions and subtractions

  1. $10160$

  2. $11060$

  3. $11160$

  4. $None\ of\ these$

Show answer
Correct Option: C
Explanation:

$ a+b=30,ab=176 \ a+b=30 \ \Rightarrow { \left( { a+b } \right) ^{ 2 } }={ \left( { 30 } \right) ^{ 2 } } $


$\Rightarrow { a^{ 2 } }+{ b^{ 2 } }+2ab=900 \ \Rightarrow { a^{ 2 } }+{ b^{ 2 } }+2\times 176=900 \ \Rightarrow { a^{ 2 } }+{ b^{ 2 } }=900-352 \ \Rightarrow { a^{ 2 } }+{ b^{ 2 } }=548$

$Now \ { a^{ 3 } }+{ b^{ 3 } }=\left( { a+b } \right) \left( { { a^{ 2 } }+{ b^{ 2 } }-ab } \right)  \ =30\left( { 548-176 } \right)  \ =30\times 372 \ =11160 $

$(308+264)cm^{2}=572cm^{2}$

maths operations adding and subtracting numbers using place value addition & subtraction mental additions and subtractions

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

$\begin{matrix} \left( { 308+264 } \right) c{ m^{ 2 } }=572c{ m^{ 2 } }   \ It\, \, is\, \, true.\, \, \, \, Ans. \  \end{matrix}$

Find the sum of $-59,\ -41,\ 73,\ -92,\ 81,\ -(-41)$ and $-3$.

maths operations adding and subtracting numbers using place value addition & subtraction mental additions and subtractions

  1. $3$

  2. $0$

  3. $1$

  4. $-2$

Show answer
Correct Option: B
Explanation:

$-59, -41, 73, -92, 81, -(-41), -3$.


$=-59+(-41)+73+(-92)+81+[-(-41)]+(-3)$.


$=-59-41+73-92+81+41-3$.

$=73+81+41-59-92-41-3$

$=195-195$

$=0$.

Subtract the second term form first term.
$5p , 11p$

maths operations adding and subtracting numbers using place value addition & subtraction mental additions and subtractions

  1. $-6p$

  2. $1p$

  3. $5p$

  4. $12p$

Show answer
Correct Option: A
Explanation:

$5p-11p=-6p$

Hence, the answer is $-6p.$

Subtract : $3x^{2}+2yx$ from $2x^{2}+3yx$

maths operations adding and subtracting numbers using place value addition & subtraction mental additions and subtractions

  1. $x^{2}-4xy$

  2. $5x^{2}y$

  3. $xy-x^{2}$

  4. $x^{2}+4xy$

Show answer
Correct Option: C
Explanation:
$(2x^{2}+3yx)-(3x^{2}+2yx)$

$=2x^{2}+3xy-3x^{2}-2xy$

$=-x^{2}+xy\Rightarrow (C)$

State whether true or false 
There is a natural number which when added to a natural number, gives that number.

maths operations adding and subtracting numbers using place value addition & subtraction mental additions and subtractions

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

We know that $0$ is the only number which, when added to some other number then it gives the same number.

Since $0$ is not a natural number then the given statement is false.