SOLUTION: The average age of a group of persons going for picnic is 16 years. Twenty new persons with an average age of 15 years join the group on the spot due to which their average age bec

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Question 1102603: The average age of a group of persons going for picnic is 16 years. Twenty new persons with an average age of 15 years join the group on the spot due to which their average age becomes 15.5 years. The number of persons initially going for picnic is :
Answer by greenestamps(13216) About Me  (Show Source):
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The average age of the entire group (15.5) is exactly halfway between the average age of the first group (16) and the average age of the second group (15).

A common sense understanding of averages tells us that the two groups must have the same number of people.

Since the second group has 20 people, the first group also has 20 people.