Question

The average weight of boys in a class is 30 kg and the average weight of girls in the same class is 20 kg. If the average weight of the whole class is 23.25 kg, what could be the possible strength of boys and girls respectively in the same class?

• A. 14 and 26
• B. 13 and 27
• C. 17 and 27
• D. None of these

Answer 1

The correct option is B 13 and 27

Let $x$ be the number of boys and $y$ be the number of girls

$\Rightarrow 23.25\times (x+y)=30x+20y$

$\Rightarrow 23.25x+23.25y=30x+20y$

$\Rightarrow 23.25x-30x=20y-23.25y$

$\Rightarrow -6.75x=-3.25y$

$\Rightarrow 6.75x=3.25y$

$\Rightarrow \frac{x}{y}=\frac{3.25}{6.75}=\frac{3.25\times 100}{6.75\times 100}=\frac{325}{675}=\frac{13}{27}$

$\therefore$the possible strength of boys and girls respectively in the same class are $13$ and $27$