Question

It costs Rs. 6000/- and Rs. 6,100- respectively to paint the 4 walls of 2 square halls, of the same height. If the length of one hall exceeds the length of the other by 1 m and the cost of painting is Rs. 5 per sq.m., what is the height of the two walls?
1. 10 m
2. 7.5 m
3. 3 m
4. 5 m

Answer 1

Correct Answer - Option 4 : 5 m

Calculation:

Let the length of the halls be 'a' and 'a + 1' respectively and height of the halls be 'h'.

Area of 4 walls of the first hall (A₁) = 4 × a × h 

Cost of painting 4 walls of first hall = (4 × a × h) × 5 = Rs 6000

⇒ 20ah = 6000      ----(1)

Area of 4 walls of the second hall (A1) = 4 × (a + 1) × h 

Cost of painting 4 walls of second hall = [4 × (a + 1) × h] × 5 = Rs 6100

⇒ 20h(a + 1) = 6100      ----(2)

(2)/(1) ⇒ (a + 1)/a = 61/60

Or, a = 60

(1) ⇒ 20 × 60 × h = 6000

Or, h = 60/12 = 5 m

∴ Height of the walls is 5 m.