Numbers Questions

Q:

A boy multiplied 987 by a certain number and obtained 559981 as his answer. If in the answer both 98 are wrong and the other digits are correct , then the correct answer would be :

 A) 553681 B) 555181 C) 555681 D) 556581

Explanation:

987 = 3 * 7 * 47.
So, the required number must be divisible by each one of 3, 7, 47
553681 => (Sum of digits = 28, not divisible by 3)
555181 => (Sum of digits = 25, not divisible by 3)
555681 is divisible by each one of 3, 7, 47.

14 7523
Q:

How many terms are in the G.P. 3, 6, 12, 24, ......., 384 ?

 A) 8 B) 9 C) 10 D) 11

Explanation:

Here a = 3 and r = 6/3 = 2. Let the number of terms be n.
Then, t = 384 => a * r^(n-1) = 384
=> 3 * 2^(n-1) = 384 => 2^(n-1) = 128 = 2^(7)

=> n-1 = 7 => n = 8.

5 6437
Q:

The sum of the two numbers is 12 and their product is 35.What is the sum of the reciprocals of these numbers?

 A) 12/35 B) 1/35 C) 35/8 D) 7/32

Explanation:

Let a and b are the numbers.Then a+b is 12 and ab is 35.

a+b/ab = 12/35

1/b + 1/a = 12/35

9 5993
Q:

What is the greatest of 3 consecutive integers whose sum is 24 ?

 A) 6 B) 7 C) 8 D) 9

Explanation:

The sum of three consecutive integers can be written as n + (n + 1) + (n + 2) = 3n + 3

If the sum is 24, we need to solve the equation 3n + 3 = 24;

=> 3n = 21;

=> n = 7

The greatest of the three numbers is therefore 7 + 2 = 9

11 5991
Q:

On dividing 2272 as well as 875 by 3-digit number N,we get the same remainder.The sum of the digits of N is:

 A) 13 B) 12 C) 11 D) 10

Explanation:

(2272-875) = 1397, is exactly divisible by N.

Now , 1397 = 11 x 127

The required 3-digit number is 127,the sum of digits is 10.

12 5902
Q:

A number when divided by 779 gives a remainder 47. By dividing the same number by 19, what would be the remainder?

Number = ( 779 x a) + 47, where "a" is the quotient

= (19 x 41 x a) + (19 x 2) + 9

= 19 x (41a + 2) + 9

= 19 x (New quotient) + 9

$\inline&space;\fn_jvn&space;\therefore$  Required remainder = 9

5801
Q:

Which one of the following cannot be the square of a natural number?

 A) 32761 B) 42437 C) 81225 D) 20164

Explanation:

The square of a natural number never ends in 7.
42437 is not the square of a natural number

10 5463
Q:

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

 A) 86 B) 94 C) 100 D) 115

Explanation:

Let the number be x.Then

60% of $\frac{3}{5}$of x=36.

=> $\frac{60}{100}*\frac{3}{5}*x=36$

=> $\frac{9x}{25}=36$ => x=$\frac{25*36}{9}=100$

Required number is 100.