Discussion

Question:

Average of 7 numbers is 25. When arranged in ascending order, average of the smallest 4 numbers is 15 and that of the largest 4 numbers is 36. Find the 4^th number?

Explanation:

The sum of all 7 numbers = 7 × 25 = 175

Average of the smallest 4 numbers = 4 × 15 = 60
Average of the largest 4 numbers = 4 × 36 = 144

⇒ Sum of all 7 numbers = Sum of smallest 4 numbers + Sum of largest 4 numbers - 4^th number
⇒ 175 = 60 + 144 - 4^th number
⇒ 4^th number = 204 - 175 = 29

Hence, option (b).

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