A boy found that the average of 20 numbers is 35 when he writes a number '61’

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Question

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

Options:

A . 37.25

B . 32.75

C . 34.25

D . 34.75

Answer: Option B
Answer: (b)Correct average = 35 - $({61 - 16}/20)$ = 35 – $45/20$ = 35 – 2.25 = 32.75 Aliter : Using Rule 26,The correct average will be = m +${\text"(a-b)"}/ \text"n"$.Here, n = 20, m = 35 a = 16, b = 61 Correct mean = m + ${\text"(a - b)"}/\text"n"$= 35 +${(16 - 61)}/20$= 35 - $45/20$= 35 – 2.25 = 32.75

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