Tag: multiplication of numbers

Questions Related to multiplication of numbers

156 $\times$ ____ = 0

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

  1. 1

  2. 0

  3. 156

  4. -1

Show answer
Correct Option: B
Explanation:

156 $\times$ 0 = 0

$(32) \times (-4) \times (-3) \times 0 \times (-6)  $ is equal to 

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

  1. +27,648

  2. +276,480

  3. 0

  4. -27,648

Show answer
Correct Option: C
Explanation:

The resultant product of $3$ negative signs would be negative.

But the numbers are multiplied with $0$.
So, the resultant product be $0$.
$\therefore (32) \times (-4) \times (-3) \times 0 \times (-6) = 0$

Find the value of $x$.
$\displaystyle \left ( -\frac {1}{4} \right )^{-3} \times \left ( \frac {1}{4} \right )^{4} \div 4^{-2}=-(4^{10x+1})$

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

  1. $\displaystyle -\frac {2}{5}$

  2. $4$

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

  4. $0$

Show answer
Correct Option: D
Explanation:

$
-{ \frac { 1 }{ 4 }  }^{ -3 }{ \times \frac { 1 }{ 4 }  }^{ 4 }\div { 4 }^{ -2 }{ \quad =\quad -4 }^{ (10x+1) }\ \ -{ 4 }^{ 3 }{ \times 4 }^{ -4 }\times { 4 }^{ 2 }{ \quad =\quad -4 }^{ (10x+1) }\ { -4 }^{ 3-4+2 }{ \quad =\quad -4 }^{ (10x+1) }\ { -4 }^{ 1 }{ \quad =\quad -4 }^{ (10x+1) }\ 1\quad =\quad 10x\quad +1\ 10x\quad =\quad 0\ x\quad =\quad 0
$

The average age of a family of 6 members 4 years ago was 25 years. Meanwhile a child was born in this family and still the average age of the whole family is same today. The present age of child is ......

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

  1. 2 years

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

  3. 1 years

  4. Data insufficient

Show answer
Correct Option: C
Explanation:

Total age of 6 family members four year ago =$25\times 6=150$years
Total age of 6 family member now=150+$4\times 6=150+24=174$years
Total age of 6 family member and child =$25\times 7=175$year
Age of child =175-174=1 year

Solve 45 % of 1500 + 35 % of 1700 = ? % of 3175

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

  1. 30

  2. 35

  3. 45

  4. 40

Show answer
Correct Option: D
Explanation:

45 % of 1500 + 35 % of 1700 = ? % of 3175
Or $\frac{45}{100}\times 1500+\frac{35}{100}\times 1700= \frac{x}{100}\times 3175$
Let x is new %

Or $45\times 1500+35\times 1700=3175\times x$
OR 67500+59500=3175x
Or x=$\frac{127000}{3175}=40%$

$102 \times 103$

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

  1. 10506

  2. 10505

  3. 1050

  4. 10504

Show answer
Correct Option: A
Explanation:

$(100 + 2) \times (100 + 3)$
           [Using $(x +a) (x+b)=x^2+(a+b)x+ ab$]
$ = (100)^2 + (2 + 3) \times 100 + 2 \times 3$
$ = 10000 + 5 \times 100 + 6 = 10000 + 500 + 6 = 10506$

A pineapple costs rs. 7. A watermelon cots rs. 5. X spends rs. 38 on these fruits. The number of pineapples purchased is _______.

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

  1. 2

  2. 3

  3. 4

  4. Data inadequate

Show answer
Correct Option: C
Explanation:

Let the number of pineapple and watermelon be x and y
Then 7x+5y=38 (given cost of pineapple and watermelon is Rs 7and Rs 5
Or 5y=38-7x
Or $y=\frac{38-7x}{5}$ 
clearly y is whole number only when (38-7x) is divisible by 5
This happens when x=4

If x is a whole number then $\displaystyle x^{2}\left ( x^{2}-1 \right )$ is always divisible by

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

  1. 12

  2. 24

  3. 12 - x

  4. Multiple of 12

Show answer
Correct Option: A
Explanation:

Putting x=2, we get $2^2\left(2^2-1\right)= 12. So, x^2\left(x^2-1\right)$ is always divisible by 12

Suresh travelled 1200 km by air which form (2/5) of his trip. One third of the whole trip, he travelled by car and the rest of the journey he performed by train. Find the distance travelled by train. Also, find the speed of the train if the time taken for the train to travel the whole distance is 8 hrs

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

  1. 1600 km, 350 km/hr

  2. 800 km, 375 km/hr

  3. 1800 km, 300 km/hr

  4. 480 km, 380 km/hr

Show answer
Correct Option: B
Explanation:

Suresh travelled 1200 km by air which form (2/5) of his trip. 
Then total distance of journey=$\frac{5}{2}\times 1200=3000 km$
Suresh travelled $\frac{1}{3}$of journey by car =$\frac{1}{3}\times 3000=1000 km$
Then suresh travelled distance by train =3000-1200-1000=800 km
If whole journey by train in 8 hours 
So speed of train=$\frac{3000}{8}$=375 km/Hr

Three lightships flash simultaneously at 6;00 a.m. The first lightship flashes every 12 seconds, the seconds lightship every 30 seconds and the third lightship every 66 seconds. At what time will the three lightships next flash together?

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

  1. 6;09 a.m.

  2. 6:10 a.m.

  3. 6:11 a.m.

  4. 6:12 a.m.

Show answer
Correct Option: C
Explanation:

Three lightships flash simultaneously at 6;00 a.m. The first lightship flashes every 12 seconds, the seconds lightship every 30 seconds and the third lightship every 66 seconds. 
Then we take common multiple of 12,30 or 66 
That is $2\times 6\times 5\times 11=660$
So  the three lightships next flash together=660 seconds =$\frac{660}{60}=11$mints
The time next flash is after 11 mints=6.11 A.M