The average of 17 numbers is 60. The average of the first 9 numbers is 55 and…
2019
The average of 17 numbers is 60. The average of the first 9 numbers is 55 and that of the last 9 numbers is 62. If the middle number is removed, what will be the new average (correct to one decimal place)?
Answer: C. 61.7 — Total of 17 numbers = 17 × 60 = 1020. Sum of first 9 numbers = 9 × 55 = 495. Sum of last 9 numbers = 9 × 62 = 558. Adding the first 9 and last 9 counts the…
- A.
62.2
- B.
61.9
- C.
61.7
- D.
62.4
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Correct answer: C
Total of 17 numbers = 17 × 60 = 1020. Sum of first 9 numbers = 9 × 55 = 495. Sum of last 9 numbers = 9 × 62 = 558. Adding the first 9 and last 9 counts the middle number twice: 495 + 558 = 1053. Middle number = 1053 − total 1020 = 33. New sum after removing the middle number = 1020 − 33 = 987. Number of remaining numbers = 16. New average = 987 ÷ 16 = 61.6875 ⇒ 61.7 (to one decimal place).