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Bunuel
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Bunuel
The average (arithmetic mean) of five numbers is 25. After one of the numbers is removed, the average (arithmetic mean) of the remaining numbers is 31. What number has been removed?

(A) 1

(B) 6

(C) 11

(D) 24

(E) It cannot be determined from the information given.

Sum of the five numbers is 125

Given, \(\frac{125 - x}{4} = 31\)

So, \(125 - x = 124\)

Or, x = 1 , Answer must be (A) 1
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Theory

    ➡ Average = Sum of all the Values / Total Number of Values
    ➡ Sum of all the Values = Average * Total Number of Values

The average (arithmetic mean) of five numbers is 25

Sum of 5 numbers = Average * 5 = 25*5 = 125

After one of the numbers is removed, the average (arithmetic mean) of the remaining numbers is 31

Sum of remaining 4 numbers = Average * 4 = 31 * 4 = 124

Discarded number = Sum of 5 numbers - Sum of remaining 4 numbers = 125 - 124 = 1

So, Answer will be A.
Hope it helps!

Watch the following video to Learn the Basics of Statistics

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