Seats for Mathematics, Physics and Biology in a school are in the ratio 5 : 7 : 8. There is a proposal to increase these seats by 40%, 50% and 75% respectively. What will be the ratio of increased seats?

Answer: Option A

Originally, let the number of seats for Mathematics, Physics and Biology be 5x, 7x and 8x respectively
Number of increased seats are (140% of 5x), (150% of 7x) and (175% of 8x)
  $$=\left(\frac{140}{100}\times 5x\right),$$     $$\left(\frac{150}{100}\times 7x\right)$$   and $$\left(\frac{175}{100}\times 8x\right)$$
$$\begin{array}{rl}& =7x,\frac{21x}{2}\text{ and }14x\\ & \therefore \text{The required ratio}\\ & =7x:\frac{21x}{2}:14x\\ & =14x:21x:28x\\ & =2:3:4\end{array}$$