Mahesh calculated his average over the last 24 tests and found it to be 76. He…
2025
Mahesh calculated his average over the last 24 tests and found it to be 76. He finds out that the marks for three tests have been inverted by mistake. The correct marks for these tests are 87, 79 and 98. What is the approximate percentage difference between his actual average and his incorrect average?
- A.
1.75
- B.
2.25
- C.
2.15
- D.
No difference
Attempted by 574 students.
Show answer & explanation
Correct answer: D
Final answer: No difference (0%).
Steps:
Original total for 24 tests = 76 × 24 = 1824.
If the recorded marks were digit-reversed, they become 78, 97 and 89.
Sum of correct marks = 87 + 79 + 98 = 264. Sum of reversed recorded marks = 78 + 97 + 89 = 264.
Because the corrected sum and the recorded sum for those three tests are equal, the overall total remains 1824 and the corrected average = 1824 ÷ 24 = 76.
Percentage difference = (correct average − incorrect average) ÷ incorrect average × 100% = (76 − 76) ÷ 76 × 100% = 0%.