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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
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- 15
- 30
- 20
- 10
- 15
Correct Option: D
Number of natural numbers = p
∴ Their sum = 15p
According to the question,
15p + 30 – 5 = p × 17.5
⇒ 17.5p – 15p = 25
⇒ 2.5p = 25
⇒ p = 25/2.5 = 10
