Multiple choice

A boy found that the average of 20 numbers is 35 when he writes a number 61 instead of 16. The correct average of 20 numbers is

  1. 32.75

  2. 37.25

  3. 34.75

  4. 34.25
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When 61 is written instead of 16, the sum increases by 61-16=45. The incorrect average is higher by 45/20 = 2.25. Incorrect average = 35, so correct average = 35 - 2.25 = 32.75. Alternatively: incorrect sum = 20×35=700, correct sum = 700-45=655, correct average = 655/20 = 32.75.

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