Question

A swimming pool is 30 m in length, 15 m in breadth and 5 m in depth
Find the cost of cementing its floor and walls at the rate of Rs 12 per
square metre​

Answer 1

A swimming pool is a cuboid, so we'll use the formula 2(LB + LH + BH) to find its surface area which is to be plastered.

However, swimming pool doesn't have a ceiling, so we don't have to consider area of top surface. we will just substract it from total area.

Required expression will look like this -

2(LB + BH + LH) - LB ( we substract LB because its area of non existent topmost side)

required area to be plastered -

2(BH + LH) + LB

= 2 (15×5 + 30×5) + (30×15)

= 2 ( 75 + 150) + 450

= 900 m²

Cost for plastering is ₹12 per sq. metre

so total cost will be ₹ (900 × 12) = ₹10,800