Question

The average of some natural numbers is 15. If 30 is added to first number and 5 is subtracted from the last number the average becomes 17.5 then the number of natural number is ?

A 10 Correct Answer Incorrect Answer
B 30 Correct Answer Incorrect Answer
C 20 Correct Answer Incorrect Answer
D 15 Correct Answer Incorrect Answer

Solution

The average of n natural number = 15
New average of n natural numbers = 17.5
ATQ,
(17.5) n = (15)n + 30 – 5
17.5n – 15n = 25
n = 10

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