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
A20
B10
C30
D15
Answer:
B. 10
Explanation:
Number of natural numbers = x sum = 15x 15x + 30 – 5 = x × 17.5 17.5x – 15x = 25 ⇒ 2.5x = 25 x =10