Question #8d811

1 Answer
Jul 1, 2016

Answer:

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#