Subject: General Aptitude · Chapter: Average · Exam: · Marks: · Difficulty:
The average of a non-zero number and its square is 5 times the number. The number is
(a)9
(b)17
(c)29
(d)295
Answer
Answer (as printed): A
Explanation
Let the number be $x$. Then, $$\begin{aligned} \frac{x+x^{2}}{2}=5 x & \Leftrightarrow x^{2}-9 x=0 \\ & \Leftrightarrow x(x-9)=0 \\ & \Leftrightarrow x=0 \text { or } x=9 . \end{aligned}$$ So, the number is 9.
Explanation as extracted from the printed page; notation may be imperfect.