The average of 10 numbers is given as 40. However, one number was mistakenly…
2025
The average of 10 numbers is given as 40. However, one number was mistakenly recorded as 40 instead of 45. What will be the correct average after correcting the mistake?
- A.
40.5
- B.
0.5
- C.
4.5
- D.
52.5
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Show answer & explanation
Correct answer: A
Key calculation:
Original total = 10 × 40 = 400.
After correcting the mistaken entry (replace 40 with 45), the total becomes 400 − 40 + 45 = 405.
New average = 405 ÷ 10 = 40.5.
Shortcut: Add the change in one number divided by the total number of items to the old average.
40 + (45 − 40) ÷ 10 = 40 + 5/10 = 40 + 0.5 = 40.5