Question

prove area of four walls of room

Answer 1

area of four walls of a room = lateral surface area = 2h( l+b )

Answer 2

four walls of room contain 2pair of congruent rectangle.

so area of one pair rectangle = 2lh
area of another pair of rectangle = 2bh
area of 4 walls of room =2lh+2bh
=2h (l+b)

:-)hope it helps u.