Question

The cost of painting a wall of dimensions 80 m × 70 m is Rs. 10 per metre square. If the length of wall is increased by 15% and breadth by 10% then what is the cost of painting the increased area of the wall?
1. Rs. 18040
2. Rs. 18400
3. Rs. 14480
4. Rs. 14840

Answer 1

Correct Answer - Option 4 : Rs. 14840

Given:

Wall of dimensions 80 m × 70 m

Cost of painting a wall of dimensions 80 m × 70 m is Rs. 10 per metre square

Formula used:

If a number is increased/decreased by x%

New number = (100 + x%)/100 × Actual number    (increase)

New number = (100 – x%)/100 × Actual number    (decrease)

Calculation:

Area of wall = 80 × 70 = 5600 m²

Increased length = 80 × 115/100 = 92m and increased breadth = 70 × 110/100 = 77m

Now, new area = 92 × 77 = 7084 m²

⇒ Increase in area = 7084 – 5600 = 1484 m²

∴ Cost of painting of increased area = 1484 × 10 = Rs. 14840