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

Parvesh Kanani • 2.84K Points
Extraordinary Math

Q. 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

(A) 19
(B) 18
(C) 20
(D) 25

Correct Answer - Option(D)

Explanation by: Parvesh Kanani

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

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