The total of the ages of a group of 150 boys is 2100, the average age of 50 of them is 12 yr and that of another 50 is 16 yr. find the average age of the remaining boys.
A) 12 yr
B) 13 yr
C) 14 yr
D) 15 yr
E) None of these
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Answer:
C) 14 yr
Step-by-step explanation:
Let m be the average age of the remaining 50 boys.
The sum of the ages of the first 50 is 50×12 = 600.
The sum of the ages of the second 50 is 50×16 = 800.
The sum of the ages of the remaining 50 is 50m.
The sum of all 150 boys' ages is then
600 + 800 + 50m = 2100
=> 50m = 2100 - 1400 = 700
=> m = 700 / 50 = 14
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