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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

A20

B10

C30

D15

Answer:

B. 10

Read Explanation:

Number of natural numbers = x sum = 15x 15x + 30 – 5 = x × 17.5 17.5x – 15x = 25 ⇒ 2.5x = 25 x =10


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