Average problem

[R.K]

out of 35 boys 7 are 4 ft 5 inches. 15 are 3 ft 6 inches and rest 4 ft. what is the average height of the boys????
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[Anurag@Gurome]

out of 35 boys 7 are 4 ft 5 inches. 15 are 3 ft 6 inches and rest 4 ft. what is the average height of the boys?

1 ft = 12 inches

Total height of 35 boys
= [7*(4 ft 5 inches) + 15*(3ft 6 inches) + 13*(4 ft)]
= [7*4 + 15*3 + 13*4] ft + [7*5 + 15*3] inches
= [28 + 45 + 52] ft + [35 + 45] inches
= 125 ft + 80 inches

Hence, average height of the boys
= (125 ft + 80 inches)/35
= (25 ft + 16 inches)/7
= (25*12 + 16)/7 inches
= 316/7 inches
= 45 and 1/7 inches
= 3ft 9 and 1/7 inches