Question

Question #8d811

Answer 1

The right answer is (b) `69`

Explanation:

Let the height of five men be `H_1`, `H_2`, `H_3`, `H_4` and `H_5`.

We know that

(1) `(H_1+H_2+H_3+H_4+H_5)/5 = 68`

(2) `H_1 = 70`

(3) `(H_2+H_3+H_4)/3 = 67`

Our task is to determine `H_5`

SOLUTION

From (1):
(4) `H_1+H_2+H_3+H_4+H_5 = 5 * 68 = 340`

From (3):
(5) `H_2+H_3+H_4 = 3*67 = 201`

Substitute (2) and (5) into (4) getting
`70+201+H_5 = 340`
from which follows
`H_5 = 340-70-201 = 69`

CHECK the average height of all five men:
`(H_1+H_2+H_3+H_4+H_5)/5 = (70+201+69)/5 = 340/5=68`