What will be the Natural Number? If

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:

  1. 20
  2. 30
  3. 15
  4. 10
Monis Rasool Professor Asked on 7th July 2015 in Maths.
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1 Answer(s)

Answer: (4) 10
Explanation:-
Let be the number of natural number is X
The average X natural number = 15
The sum of X natural number = 15 x X = 15X
30 is added to first number and 5 is subtracted from the last number.
Then, the sum of X natural number = 15X + 30 – 5 = 15X + 25
Then, average = (15X + 25 ) /X = 17.5
= 15X +  25 = 17.5X
2.5X = 25
X = 10
Hence, the number of natural number is 10.

Anurag Mishra Professor Answered on 8th July 2015.
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