Out of four numbers, the average of the first three is 18

Home » Aptitude » Average » Question

Out of four numbers, the average of the first three is 18 and that of the last three is 16. If the last number is 19, the first is

1. 19
2. 18
3. 20
4. 25

Correct Option: D

Here , Sum of first three = 18 × 3
⇒ a + b + c = 54
and Sum of last three = 16 × 3
⇒ b + c + d = 48
last number = 19
∴ a + b + c – b – c – d
⇒ 54 – 48 = 6
⇒ a – d = 6
⇒ a – 19 = 6
⇒ a = 19 + 6 = 25