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Subject :IMO    Class : Class 9

In a school, there are 40 students in which boys and girls are in the ratio 3 : 1. The mean age of the boys is 20 years and the mean age of the girls is 18 years. If there is increase in girls by 5 and decrease in boys by 10, then find the new average age (approx.) when the students joining or leaving doesn't change the average age of boys and girls respectively.

A 15 years
B 19 years
C 16 years
D Can't say

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