Fifty Members of Group

The average age of a group of 50 people is 45. Three members, ages 50, 60, and 72, leave the group. What is the average age of the remaining 47 people?


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If we know that the average of 50 ages is 45, we also know that the sum of the 50 ages is 50 · 45 = 2250. (This is a useful bright idea.)

The three people who left have a total age of 50 + 60 + 72 = 182.

We subtract: 2250 – 182 = 2068. This is the sum of the ages of the remaining 47 folks, so we divide 2068 by 47 and we get 44 as the new average age.

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