Question
The average age of (x + 7) trainees is 17 years. When a
39-year-old trainer joins, the average becomes 18 years. Find x% of 500.Solution
Total age = 17(x + 7)
According to question,
[17(x + 7) + 39] = 18(x + 7 + 1)
17x + 119 + 39 = 18x + 144
18x - 17x = 158 - 144
x = 14
So, 14% of 500 = 70
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