Question

Find the cost of painting 15 cylindrical pillars of a building at Rs 2.50 per square metre if the diameter and height of each pillar are 48 cm and 7 metres respectively.

Answer 1

Diameter = 48 cm
Radius = 24 cm = 0.24 m
Height = 7 m

Now, we have:
Lateral surface area of one pillar$=\mathrm{\pi dh}=\frac{22}{7}\times 0.48\times 7=10.56{\mathrm{m}}^2$
Surface area to be painted = total surface area of 15 pillars $=10.56\times 15=158.4m^2$
∴ Total cost$=\mathrm{Rs}(158.4\times 2.5)=\mathrm{Rs}396$