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Your question is – Andrew had 4 children. One of his children was found to be dead due to some accident. At this time the average age of all his 4 children was 16 years. What will be the average age of the remaining children of Andrew, after a time period of 7 years of the death of his child?

I have solved this problem thus, you can read my Explanation for your better understanding:

According to  the question,
Total number of children Andrew had = 4 …..i
The average of all his 4 children = 16 years …..ii

∴ The sum of the ages of all his 4 children = 16*4 = 64 …..iii

And, sum of the ages of children after the death of 1 child = 16*3 = 48 …..iv

Now, sum of the ages of the remaining children after 7 years of the death of 1 child of
Andrew = 48 + (3*7) = 48+21 = 69 …..v

Thus, the average age of his remaining 3 children after 7 years of death of his 1 child =
69/3 = 23 …..vi

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