The floor of an office has dimensions 5m × 3m. the cost of painting the walls and celling is Rs 7,440 at the rate of Rs 60/m². Find the height of the room (in m). (rounded off to one decimal place)

Correct option is D

Given:

Dimension of the floor: 5m × 3m = 15 m² 

Cost of painting: Rs. 7440

Rate of painting: Rs. 60/m² 

Formula Used: 

Area of four walls = $$2\times h(l+b)$$ 

where, h = height, l = length, b = breadht

Solution:

Area to be painted = $$\frac{Total\ cost}{Rate}$$ = $$\frac{7440}{60}$$ = 124m²​

Ceiling area = 5m × 3m = 15 m²

Wall area = 124 -15= 109m²​

Wall area =  2×(length × h) + 2×(breadth × h) 

length = 5m and breadth = 3m 

2(5h) + 2(3h) = 109

10h+6h = 109

16h = 109

h = $$\frac{109}{16}$$ = 6.8m

Thus the correct answer is (D)