Subject: General Aptitude · Chapter: Average · Exam: · Marks: · Difficulty:
If the mean of 5 observations $x, x+2, x+4, x+$ 6 and $x+8$ is 11, then the mean of the last three observations is
(a)11
(b)13
(c)15
(d)17
Answer
Answer (as printed): B
Explanation
We have : $\left[\frac{x+(x+2)+(x+4)+(x+6)+(x+8)}{5}\right]=11$ or $5 x+20=55$ or $x=7$. So, the numbers are 7, 9, 11, 13, 15. $$\therefore \quad \text { Required mean }=\left(\frac{11+13+15}{3}\right)=\frac{39}{3}=13 .$$
Explanation as extracted from the printed page; notation may be imperfect.