Question
Average of first 3 numbers is half the average of next 6
numbers. If the average of all 9 numbers is 15, find the sum of the last 6 numbers.Solution
Let the sum of the last 6 numbers be 'n'.
(sum of first 3 numbers) ÷ 3 = 0.5 × (n/6)
⇒ Sum of first 3 numbers = 0.25n
Total sum = n + 0.25n = 1.25n
Average of 9 numbers = 1.25n ÷ 9 = 15
⇒ 1.25n = 135
⇒ n = 108
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