Question

Mean of eight numbers is $38.4$ and the mean of seven of them is $39.2$. What is the eight number?

• A. $34.8$
• B. $32.8$
• C. $0.8$
• D. None of these

Answer 1

The correct option is B $32.8$

Given that,

mean of 8 numbers = 38.4 ...(i)

mean of 7 numbers = 39.2 ...(ii)

We know that,

mean of n numbers = $\frac{Sumofnnumbers}{n}$

Therefore, using (i),

$38.4=\frac{Sumof8numbers}{8}$

$\Rightarrow$ sum of 8 numbers = $38.4\times 8$

$=307.2$

similarly, using (ii)

Sum of 7 numbers $=39.2\times 7$

$=274.4$

therefore, eight numbers=

Sum of 8 numbers - sum of 7 numbers

$\Rightarrow 307.2-274.4$

$\Rightarrow 32.8$