Let ABCD be the rectangular field and PQRS and KLMN be the two rectangular roads with width 2 m and 2.5 m, respectively.
Length of the rectangular field, CD = 115 cm
Breadth of the rectangular field, BC = 64 m
∴ Area of the rectangular lawn ABCD = 115 m × 64 m = 7360 m2
Area of the road PQRS = 115 m × 2 m = 230 m2
Area of the road KLMN = 64 m × 2.5 m = 160 m2
Clearly, the area of EFGH is common to both the two roads.
∴ Area of EFGH = 2 m × 2.5 m = 5 m2
∴ Area of the roads = Area (KLMN) + Area (PQRS) − Area (EFGH)
= (230 m2 + 160 m2) − 5 m2 = 385 m2
Rate of gravelling the roads = Rs 60 per m2
∴ Total cost of gravelling the roads = Rs (385 × 60)
= Rs 23,100