The average of some natural numbers is 27. If 69 is added to the first number and 12 is subtracted from the last number, the average becomes 32.7, then the number of natural numbers is:
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 10.
Let the number of natural numbers = n
Sum = 27n
After changes, new sum = 27n + 69 - 12 = 27n + 57
New average = 32.7
So,(27n + 57) / n = 32.7
27n + 57 = 32.7n
57 = 32.7n - 27n = 5.7n
n = 57 / 5.7 = 10