A rectangular lawn, 75 m by 60 m, has two roads, each road 4 m wide, running through the middle of the lawn,

Area of rectangle ABCD = Length × Breath
= 75 × 4
= 300 m2

Area of rectangle PQRS = Length × Breath
= 60 × 4
= 240 m2

Area of square EFGH = (side)2
= (4)2
= 16 m2

∴ Area of the footpath = Area of rectangle ABCD + Area of rectangle PQRS − Area of square EFGH
 = 300 + 240 − 16
 = 524 m2

The cost of gravelling the road per m2 = Rs 50
The cost of gravelling the roads 524 m2 = Rs 50 × 524
= Rs 26200

Hence, the total cost of gravelling the roads at Rs 50 per m2 is Rs 26200.