Question
Average of first 5 numbers is 4 times the average of
next 4 numbers. If the average of all 9 numbers is 36, find the sum of the last 4 numbers.Solution
Let the sum of the last 4 numbers be 'n'.
(sum of first 5 numbers) ÷ 5 = 4 × (n/4)
⇒ sum of first 5 numbers = 5n
Total sum = 5n + n = 6n
Average = (6n)/9 = 36
⇒ 6n = 324
⇒ n = 54
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