Question

If the mean a, b, c, d and e is 28, mean of a, c and e is 24 and mean of b and d is $n^2-2$, then the value of n is $\pm k$, where k is

• A. 6
• B. 7
• C. 4
• D. 8

Answer 1

The correct option is A 6

Mean of a, b, c, d and e = 28
i.e., $\frac{a+b+c+d+e}{5}=28$
$\Rightarrow$ a + b + c + d + e = 140 ........ (i)
Mean of a, c and e = 24
i.e., $\frac{a+c+e}{3}=24$
$\Rightarrow$ a + c + e = 72 ........ (ii)
Subtracting (ii) from (i), we get
b + d = 68
Mean of b and d $=\frac{b+d}{2}=\frac{68}{2}=34$
$\therefore n^2-2=34\Rightarrow n^2=34+2$
$\Rightarrow n=\pm 6$