# Numbers Aptitude Test Paper 3

11) A boy was asked to multiply a number by 25 but by mistake he multiplied by 45 and the answer was 200 more than the correct answer. What was the number?

1. 7
2. 8
3. 10
4. 12 12) A number when multiplied by 16 increases by 540. What is the number?

1. 30
2. 36
3. 42
4. 46

Let the number is X.

As per question; 16X - X = 540

∴15X = 540 13) The sum of first n odd natural numbers is be given by;

1. (n+1)2
2. n2 + 1
3. n2
4. n2 - 1

First n odd natural numbers are 1, 3, 5, 7, 9. (2n-1)

The series of numbers is an arithmetic progression where the first term is 1 and the last term is 2n - 1.

Apply formula; Sn =n2( first term + last term)

∴Sn =n2[(1 + (2n - 1)]

=n2*2n = n2

14) Which of the following numbers is a prime number?

1. 167
2. 213
3. 350
4. 437

Step 1: Find a whole number 'X' for each number such that X2 > the number;

132 > 167

152 > 213

192 > 350

212 > 437

Step 2: Get all the prime numbers which are less than 'X'.

Prime numbers less than 13 are 2, 3, 5, 7, and 11

Prime numbers less than 15 are 2, 3, 5, 7, 11, and 13

Prime numbers less than 19 are 2, 3, 5, 7, 11, 13, and 17

Prime numbers less than 21 are 2, 3, 5, 7, 11, 13, 17, and 19

Step 3: Check divisibility of each number with prime numbers which are less than 'X'.

167 is not divisible by any prime number

213 is divisible by 3

352 is divisible by 2 and 11

437 is divisible by 19

∴167 is the required prime number as it is not divisible by any prime number.

15) Which of the following is the result of 1505 x 1505?

1. 2265015
2. 2265035
3. 2265045
4. 2265025

Apply formula; (a + b)2 = a2 + b2 + 2ab

1505 x 1505

=15052

= (1500 + 5)2

=15002 + 52 + 2 *1500* 5

= 2250000 + 25 + 15000

= 2265025   