Question

Find the total cost to paint external areas of all the 4 walls of a room with length, breadth and height as 10 cm, 20 cm and 5 cm respectively at the rate of ₹10 per sq. metre.

Answer 1

Given,
$l=10$ cm, $b=20$ cm and $h=5$ cm

The lateral surface area of Cuboid
$=2h(l+b)$
$=2\times 5(20+10)$
$=2\times 5\times 30$
$=300{\text{cm}}^2$

(Since only the 4 walls are being considered, the 2$lb$ from total surface area has been removed)

So, total cost required to paint the external areas of 4 walls
$=300\times 10$
$=₹3000$