Q. Out of four numbers, the average of the first three is 15 and that of the last three is 16. If the last number is 19, the first is
✅ Correct Answer: (C)
16
Explanation: Given , Sum of first 3 numbers = 15 × 3 = 45
⇒ a + b + c = 45 ,
last number = d = 19
and Sum of the last three numbers = 16 × 3 = 48
⇒ b + c + d = 48
⇒ b + c = 48 – 19 = 29
∴ a + b + c = 45
⇒ a = 45 – 29 = 16
Explanation by: Parvesh Kanani
Given , Sum of first 3 numbers = 15 × 3 = 45
⇒ a + b + c = 45 ,
last number = d = 19
and Sum of the last three numbers = 16 × 3 = 48
⇒ b + c + d = 48
⇒ b + c = 48 – 19 = 29
∴ a + b + c = 45
⇒ a = 45 – 29 = 16
⇒ a + b + c = 45 ,
last number = d = 19
and Sum of the last three numbers = 16 × 3 = 48
⇒ b + c + d = 48
⇒ b + c = 48 – 19 = 29
∴ a + b + c = 45
⇒ a = 45 – 29 = 16