Question

The mean weight of $25$ students of a class is $48$ kg. If the mean weight of first $13$ students is $50$ kg. and the last $13$ students is $46$ kg. Find the weight of the 13${}^{th}$ student.

• A. $45$ kg
• B. $46$ kg
• C. $47$ kg
• D. $48$ kg

Answer 1

Answer: (D)

$48$ kg

Let the weight of 13th student $=x$
Weight of $25$ students $=25\times 48=1200$
Weight of first $13$ students $=13\times 50=650$
Weight of last $13$ students $=13\times 46=598$
Weight of first $13$ students $+$ weight of last $13$ students $=$ Weight of $25$ students $+$ weight of $13$th student
$\Rightarrow 650+598=1200+x$
$\Rightarrow x=48$

Hence, the weight of ${13}^{th}$ student is $48$ kg.