Question

The cost of painting a wall of dimensions 100 m × 70 m is Rs. 10 per metre square. If the length of wall is increased by 10% and breadth also by 10% then what is the cost of painting the increased area of the wall in rupees?
1. 17400
2. 14000
3. 17000
4. 14700

Answer 1

Correct Answer - Option 4 : 14700

Given:

Wall of dimensions 100 m × 70 m

Cost of painting a wall of dimensions 100 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 = 100 × 70 = 7000 m²

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

Now, new area = 110 × 77 = 8470 m²

⇒ Increase in area = 8470 – 7000 = 1470 m²

∴ Cost of painting of increased area = 1470 × 10 = Rs. 14700