A swimming pool is of dimensions 25 m × 12 m × 5.5 m. What is the cost of cementing its floor and wall at the rate of Rs 12.50 per square metre?

Length (l) of the swimming pool = 25 m

Breadth (b) of the swimming pool = 12 m 

Height (h) of the swimming pool = 5.5 m

The area of the four walls as well as the floor of the swimming pool is given by 2h (l + b) + lb.

$=\left[2\times 5.5\times \left(25+12\right)+25\times 12\right] {\mathrm{m}}^2$

$=\left(407+300\right) {\mathrm{m}}^2$

$=707 {\mathrm{m}}^2$

Cost of cementing 1 m² of area = Rs 12.50

∴ Cost of cementing 707 m² of area = Rs (707 × 12.50) = Rs 8837.50

Thus, the cost of cementing the floor and the wall of the swimming pool is Rs 8837.50.