A rectangular lawn 80 m × 60 m has two roads each 10 m wide running in the middle of it, one parallel to the length and the other parallel to the breadth. Find the cost of gravelling them at ₹ 1.20 per sq. metre.

To find the cost of gravelling the roads on the rectangular lawn, we first need to calculate the area of the roads.

Dimensions of the Lawn

The lawn measures:

• Length: 80 m
• Breadth: 60 m

Calculating the Area of the Roads

There are two roads, each 10 m wide:

• One road runs parallel to the length (80 m) and is 10 m wide.
• The other road runs parallel to the breadth (60 m) and is also 10 m wide.

Area of Each Road

The area of the road parallel to the length:

Area = Length × Width = 80 m × 10 m = 800 sq. m

The area of the road parallel to the breadth:

Area = Breadth × Width = 60 m × 10 m = 600 sq. m

Overlapping Area

Since the two roads overlap in the middle, we need to subtract this overlapping area:

Overlapping area = Width of road × Width of road = 10 m × 10 m = 100 sq. m

Total Area of the Roads

Now, we can calculate the total area of the roads:

Total area = Area of road 1 + Area of road 2 - Overlapping area

Total area = 800 sq. m + 600 sq. m - 100 sq. m = 1300 sq. m

Cost of Gravelling

The cost of gravelling is ₹ 1.20 per square metre. Therefore, the total cost is:

Total cost = Total area × Cost per sq. m = 1300 sq. m × ₹ 1.20 = ₹ 1560

Final Answer

The cost of gravelling the roads is ₹ 1560.