A rectangular lawn `60 mxx40 m` has two roads each 5 m wide running in the middle of in, one parallel to length and the other parallel to breadth. The cost of gravelling the roads at 80 paise per sq. m is:

Options

A. `₹380`
B. `₹385`
C. `₹400`
D. none of these

Answer

To solve the problem, we need to find the area of the two roads running through the rectangular lawn and then calculate the cost of gravelling those roads.

### Step-by-Step Solution:

1. **Identify the dimensions of the lawn:**
- Length of the lawn (L) = 60 m
- Breadth of the lawn (B) = 40 m
- Width of each road (w) = 5 m

2. **Calculate the area of the lawn:**
- Area of the lawn = Length × Breadth = 60 m × 40 m = 2400 m²

3. **Calculate the area of the roads:**
- There are two roads: one parallel to the length and one parallel to the breadth.
- Area of the road parallel to the length:
- Length of the road = Length of the lawn = 60 m
- Width of the road = 5 m
- Area of this road = Length × Width = 60 m × 5 m = 300 m²
- Area of the road parallel to the breadth:
- Breadth of the road = Breadth of the lawn = 40 m
- Width of the road = 5 m
- Area of this road = Breadth × Width = 40 m × 5 m = 200 m²

4. **Calculate the total area of the roads:**
- Total area of the roads = Area of road parallel to length + Area of road parallel to breadth
- Total area of the roads = 300 m² + 200 m² = 500 m²

5. **Adjust for the overlapping area:**
- The area where the two roads overlap (the intersection) is a square of side equal to the width of the road (5 m).
- Area of the overlapping section = Width × Width = 5 m × 5 m = 25 m²

6. **Calculate the effective area to be gravelled:**
- Effective area to be gravelled = Total area of the roads - Area of the overlapping section
- Effective area to be gravelled = 500 m² - 25 m² = 475 m²

7. **Calculate the cost of gravelling:**
- Cost per square meter = 80 paise = 0.80 rupees
- Total cost = Effective area to be gravelled × Cost per square meter
- Total cost = 475 m² × 0.80 rupees/m² = 380 rupees

### Final Answer:
The cost of gravelling the roads is **380 rupees**.