Tag: multiplication of numbers

Questions Related to multiplication of numbers

Which natural number is nearest to $9217$, which is completely divisible by $88$ ?

maths ways to multiply and divide mental multiplication multiplication methods multiplication of numbers

  1. $9152$

  2. $9240$

  3. $9064$

  4. $9184$

Show answer
Correct Option: B
Explanation:

On dividing we get,
$\frac { 9217 }{ 88 } =104\frac { 65 }{ 88 } $

Therefore,

Required number 

$= 9217 + (88 - 65)$ ,Because (88 - 65) < 65.

$= 9217 + 23$

$= 9240$

Find the value of A and B in the following sum:
$3 B$
$\underline {\times A}$
$\underline {2 5 2}$

maths ways to multiply and divide mental multiplication multiplication methods multiplication of numbers

  1. $B=6,A=7$

  2. $B=4,A=3$

  3. $B=3,A=4$

  4. $B=7,A=6$

Show answer
Correct Option: A
Explanation:

Now as $A \times B$ gives 2 in the product, the combinations could be

$2\times 1$ or $1 \times 2, 6 \times 2$ or $2\times 6, 3 \times 4$

or $4 \times 3, 6 \times 7$ or $7 \times 6$ or $8 \times 4$ or

$4\times 8, 9 \times 8$ or $8\times 9$. But to get 2 in hundred's

place and 5 in ten's place in the product, B has to be 6 and A has to be

7. Then $6\times 7=42$.
Write 2 and carry over 4. then $7\times 3= 21$ and add 4 to get 2 and 5 in the product.
The value of B is 6 and A is 7.

The least number which on division by 35 leaves a remainder 25 and on division by 45 leaves the remainder 35 and on division by 55 leaves the remainder of 45 is

maths ways to multiply and divide mental multiplication multiplication methods multiplication of numbers

  1. 2515

  2. 3455

  3. 2875

  4. 2785

Show answer
Correct Option: B
Explanation:

$35=5\times7$
$45=3\times3\times5$
$55=5\times11$
LCM of (35,45,55)=$3\times3\times5\times\times7\times11=3465$
Since difference between divisor and remainder is 10
Hence least number is $3465-10=3455$

An integer is multiplied by 2 and the result is then multiplied by 5 The final result could be

maths ways to multiply and divide mental multiplication multiplication methods multiplication of numbers

  1. 64

  2. 32

  3. 12

  4. 30

Show answer
Correct Option: D
Explanation:

If a number is multiplied by 2 and 5 respectively. Then number should be divided by their L.C.M i.e  by 10.
Clearly, only number divisible by 10 is 30.
Hence, option D is correct.

If $\displaystyle a=(2^{-2}-2^{-3}),b=(2^{-3}-2^{-4})and: c=(2^{-4}-2^{-2})$ then find the value of 3 abc

maths ways to multiply and divide mental multiplication multiplication methods multiplication of numbers

  1. $\displaystyle \frac{-63}{1024}$

  2. $\displaystyle \frac{-63}{2048}$

  3. $\displaystyle \frac{-9}{2048}$

  4. $\displaystyle \frac{9}{1024}$

Show answer
Correct Option: C
Explanation:

$a=(2^{-2}-2^{-3}),b=(2^{-3}-2^{-4})and: c=(2^{-4}-2^{-2})$
So,  $3abc=3\times (2^{ -2 }-2^{ -3 })\times (2^{ -3 }-2^{ -4 })\times (2^{ -4 }-2^{ -2 })$
$3abc=3\times (1/4-1/8)\times (1/8-1/16)\times (1/16-1/4)$
$3abc=3\times (1/8)\times (1/16)\times (-3/16)$
$3abc=\frac { -9 }{ 2048 } $
Answer (C) $\displaystyle \frac{-9}{2048}$

Simplify : $\displaystyle\frac{9^{5/2}-3\times7^0-\begin{pmatrix}\displaystyle\frac{1}{81}\end{pmatrix}^{-\displaystyle\frac{1}{2}}}{(27)^{2/3}-\begin{pmatrix}\displaystyle\frac{8}{27}\end{pmatrix}^{2/3}}$

maths ways to multiply and divide mental multiplication multiplication methods multiplication of numbers

  1. $0$

  2. $16$

  3. $27$

  4. $77$

Show answer
Correct Option: C
Explanation:

$
\frac { { 9 }^{ \frac { 5 }{ 2 }  }-{ 3\times 7 }^{ 0 }{ \quad -\frac { 1 }{ 81 }  }^{ -\frac { 1 }{ 2 }  } }{ { 27 }^{ \frac { 2 }{ 3 }  }-(\frac { 8 }{ 27 } )^{ \frac { 2 }{ 3 }  } } \quad \quad \ \ NR\quad =\quad { 3 }^{ 2\times \frac { 5 }{ 2 }  }-3-(\frac { 1 }{ 81 } )^{ -\frac { 1 }{ 2 }  }\quad =\quad { 3 }^{ 5 }-3-({ 3 }^{ -4\times \frac { -1 }{ 2 }  })\quad =243-3-9=\quad 231\quad \ Dr\quad =\quad { 3 }^{ 3\times \frac { 2 }{ 3 }  }-(\frac { 2 }{ 3 } )^{ 3\times \frac { 2 }{ 3 }  }\quad =\quad 9\quad -\quad \frac { 4 }{ 9 } \quad =\quad 77/9\ \frac { Dr }{ Nr } \quad =\quad \frac { 231 }{ 77/9 } \quad =\quad 3\times 9\quad =\quad 27
$

If $\div$ means $-$, $-$ means $\times$, $\times$ means $+$ and $+$ means $\div$, then
$20\times 60\div 40-20+10=$

maths ways to multiply and divide mental multiplication multiplication methods multiplication of numbers

  1. $40$

  2. $0$

  3. $80$

  4. $60$

Show answer
Correct Option: B
Explanation:

$20\times 60\div 40-20+10=$
After putting the true sign, we get
$20+ 60- 40\times20\div10=$
$20+60-80=$
$0=0$
Answer (B) 0

If $\displaystyle 15\frac {2}{3}\times 3\frac {1}{6}+6\frac {1}{3}=11\frac {7}{18}+x$, then the value of $x$ is ______ .

maths ways to multiply and divide mental multiplication multiplication methods multiplication of numbers

  1. $\displaystyle 39\frac {5}{9}$

  2. $\displaystyle 137\frac {4}{9}$

  3. $\displaystyle 29\frac {7}{9}$

  4. $\displaystyle 44\frac {5}{9}$

Show answer
Correct Option: D
Explanation:

$15\frac{2}{3}\times 3\frac{1}{6}+6\frac{1}{3}= 11\frac{7}{18}+x$
Or $\frac{47}{3}\times \frac{19}{6}+\frac{19}{3}= \frac{205}{18}+x$
Or $\frac{893}{18}+\frac{19}{3}= \frac{205}{18}+x$
Or 893+114=205+18x
Or 18x=893+114-205=$\frac{802}{18}=44\frac{5}{9}$

There were $50$ people at the birthday party. John invited $125$ people. Among those who attended, only $36\%$ brought gifts. How many guests brought gifts?

maths ways to multiply and divide mental multiplication multiplication methods multiplication of numbers

  1. $125$ people

  2. $50$ people

  3. $18$ people

  4. $32$ people

Show answer
Correct Option: C
Explanation:

Invited people=125
people attended birthday party=50
As per question, 36% brought gifts
$G=50\times \frac { 36 }{ 100 } $
$G=18$
Answer (C) 18

The value of $\displaystyle\frac{2^{n+4}-2\times2^{n}}{2\times2^{(n+3)}}+2^{-3}$ is equal to ........... 

maths ways to multiply and divide mental multiplication multiplication methods multiplication of numbers

  1. $2^{n+1}$

  2. $\begin{pmatrix}\displaystyle\frac{9}{8}-2^{n}\end{pmatrix}$

  3. $\begin{pmatrix}-2^{n+1}+\displaystyle\frac{1}{8}\end{pmatrix}$

  4. $1$

Show answer
Correct Option: D
Explanation:

$\displaystyle\frac{2^{n+4}-2\times2^{n}}{2\times2^{(n+3)}}+2^{-3}$
$\frac { 2^{ n+4 }-2^{ n+1 } }{ 2^{ (n+4) } } +2^{ -3 }$
$\frac { 2^{ n }(2^{ 4 }-2^{ 1 }) }{ 2^{ n }\times { 2 }^{ 4 } } +2^{ -3 }$
$\frac { (2^{ 4 }-2^{ 1 }) }{ { 2 }^{ 4 } } +2^{ -3 }$
$\frac { (16-2) }{ 16 } +\frac { 1 }{ 8 } $
$\frac { 14 }{ 16 } +\frac { 1 }{ 8 } $
$\frac { 14+2 }{ 16 } =1$
Answer (D) 1