The average of non-zero number and its square is 5 times the number. The number is__________?

A. 9
B. 17
C. 29
D. 295

Explanation:

Let the number be x. Then,

(x + x2)/2 = 5x => x2 – 9x = 0
=> x(x – 9) = 0
=> x = 0 or x = 9
So, the number is 9