There are five boxes in a cargo hold. The weight of the first box is 200 kg and the weight of the second box is 20% more than the weight of third box, whose weight is 25% more than the first box’s weight. The fourth box at 350 kg is 30% lighter than the fifth box. The difference in the average weight of the four heaviest boxes and the four lightest boxes is-

Answer: Option C

Weight of first box = 200 kg
Weight of third box
= 125 % of 200 kg
= 250 kg
Weight of second box
= 120% of 250 kg
= 300 kg
Weight of fourth box = 350 kg
Let the weight of fifth box be x kg
Then, 70% of x = 350 kg
$$\begin{array}{rl}& \Rightarrow x=\left(\frac{350\times 100}{70}\right)\\ & \Rightarrow x=500\text{ kg}\end{array}$$.
Average weight of four heaviest boxes
$$\begin{array}{rl}& \text{ = }\left(\frac{500+350+300+250}{4}\right)\text{kg}\\ & \text{ = 350 kg}\end{array}$$
Average weight of four lightest boxes
$$\begin{array}{rl}& =\left(\frac{200+250+300+350}{4}\right)\text{kg}\\ & =275\text{ kg}\end{array}$$
∴ Required difference
= (350 - 275)
= 75 kg