The average of 6 values is 12. A number is removed and the average increases by 1. Find the number removed.
Explanation:
Let x be the value of number removed.
Given, (6 × 12 - x)/5 = 13
⇒ 72 - x = 65
⇒ x = 7.
Alternately,
Had the number removed been same as average (i.e. 12), the average of remaining 5 numbers would not have changed.
Since average of now 5 numbers increases by 1 ⇒ the total increase for remaining numbers = 5 × 1 = 5.
This means that the number removed was 5 less than the old average.
⇒ x = 12 – 5 = 7
Hence, option (a).
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