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CAT 2019 Slot 2 · Quant · Averages · easy

The average of the first seven numbers is 40 and the average of the last seven numbers is 52. What is the seventh number?

Single correct option

The average of 13 numbers is 45. The average of the first seven numbers is 40 and the average of the last seven numbers is 52. What is the seventh number?
  1. A. 55
  2. B. 57
  3. C. 59
  4. D. 61
Show answer and solution

Answer: (C) 59

Sum of all 13 = 13 × 45 = 585.

Sum of first seven = 7 × 40 = 280; sum of last seven = 7 × 52 = 364.

The seventh number is counted in both groups, so 280 + 364 = 585 + (seventh number) → seventh = 644 − 585 = 59.
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Original question written in the CAT 2019 Slot 2 pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake