Question

A classroom is 7m long,6.5 m wide,4m high.it has one door 3m *1.4 m and three windowseach measuring 2m *1m.the interior walls are to be colour washed.the contractor charges rs 5.25 per m square.find the cost of colour washing

Answer 1

Length of classroom = 7m
Breadth = 6.5m
Height = 4m

Area of four walls = 2(l+b)*h

2(7m+6.5m)*4m
27 * 4 m²
108 m²

Area of door = 3m * 1.4m = 4.2 m²
Area of three windows = 3(2m * 1m)
= 3* 2m²=6m²
Area excluding door and windows
= 108 m² - (4.2 m²+6m²)
= 108 m²- 10.2m²=97.8m²

Cost of colour washing @ 5.25/m²
= 97.8 * 5.25 = 513.45

Answer 2

Answer:

We have,

Area of four walls without any gap = 2(l+b)h = 2×(6.5+7)×4 m² = 108 m²

Area of door = 3 × 1.4 m² = 4.2 m²

Area of three windows = 3×(2×1)m² = 6 m²

______________________

•°• Area to be colour washed = (Area of four walls inclusive of doors and windows) - (Area of the door + Area of three windows)

$\implies$ Area to be colour washed = [108 - (4.2+6)] m² = 97.8 m²

______________

Rate of colour washing is Rs 5.25 per square meter.

•°• Cost of colour washing = Rs (97.8 × 5.25)

= Rs. 513.45