# Numbers Aptitude Test Paper 4

16) Which of the following is the output of 495 * 495 - 105 * 105?

1. 234000
2. 360000
3. 300000
4. 350000

Apply formula; (a2 - b2) = (a - b) (a+b)

495 x 495 - 105 x 105

= (4952 - 1052)

= (495 - 105) (495 + 105)

= 390 * 600

= 234000

17) What is the unit digit in the product of 853 * 1346 * 452 * 226?

1. 4
2. 5
3. 6
4. 8

Pick up the unit digit of each number and multiply them;

3 in 853

6 in 1346

2 in 452

6 in 226

∴3 * 6 * 2 * 6 = 216 (consider the unit digit in the product)

So, the unit digit in the product of 853 * 1346 * 452 * 226 is 6.

18) If two-third of three-fourth of a number is 34, find the 20% of that number?

1. 13
2. 13.6
3. 14
4. 14.6

Let the number is X.

As per question; 19) What is the sum of all odd numbers up to 240?

1. 14400
2. 13400
3. 12400
4. 11400

Number of odd numbers up to 240 =2402= 120

Sum of first n odd numbers = n2

n = 120

Required sum = 1202 = 14400

20) What are the different prime factors of 2400?

1. 2
2. 3
3. 4
4. 5

L.C.M of 2400 = 2 x 2 x 2 x 2 x 2 x 3 x 5 x 5

The different prime factors are 3 (2, 3 and 5).   