Subject: General Aptitude · Chapter: Average · Exam: · Marks: · Difficulty:
A student was asked to find the arithmetic mean of the numbers 3, 11, 7, 9, 15, 13, 8, 19, 17, 21, 14 and $x$. He found the mean to be 12. What should be the number in place of $x$ ?
(a)3
(b)7
(c)17
(d)31
Answer
Answer (as printed): B
Explanation
Clearly, we have $$\left(\frac{3+11+7+9+15+13+8+19+17+21+14+x}{12}\right)=12$$ or $137+x=144 \quad$ or $\quad x=144-137=7$.
Explanation as extracted from the printed page; notation may be imperfect.