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

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
$$\eqalign{ & \Rightarrow x = \left( {\frac{{350 \times 100}}{{70}}} \right) \cr & \Rightarrow x = 500{\text{ kg}} \cr} $$.
Average weight of four heaviest boxes
$$\eqalign{ & {\text{ = }}\left( {\frac{{500 + 350 + 300 + 250}}{4}} \right){\text{kg}} \cr & {\text{ = 350 kg}} \cr} $$
Average weight of four lightest boxes
$$\eqalign{ & = \left( {\frac{{200 + 250 + 300 + 350}}{4}} \right){\text{kg}} \cr & = 275{\text{ kg}} \cr} $$
? Required difference
= (350 - 275)
= 75 kg