Question
The average age of a group of four children is 11 years.
From the group, one child, whose age was 6 years more than the average age, left. Four new children, whose average age is 5 years more than the given average age, join the group. Find the new average age.Solution
Initial sum of the ages of 4 children = 11 x 4 = 44 years Age of the child leaving: 11 + 6 = 17 years Sum of the ages after one child left = 44 – 17 = 27 years Sum of the ages of 4 new children = (11 + 5) x 4 = 64 years Total sum of the ages with new children = 27 + 64 = 91 years Number of children now = 4 - 1 + 4 = 7 New average age = 91/7 = 13 years
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