Question:
A cloassroom is 11 m long, 8 m wide and 5 m high. Find the sum of the areas of its floor and the four walls (including doors, windows, etc.)
Solution:
Lenght of the classroom $=11 \mathrm{~m}$
Width $=8 \mathrm{~m}$
Height $=5 \mathrm{~m}$
We have to find the sum of the areas of its floor and the four walls (i.e., like an open box).
$\therefore$ The sum of areas of the floor and the four walls $=($ length $\times$ width $)+2 \times($ width $\times$ height $+$ length $\times$ height $)$
$=(11 \times 8)+2 \times(8 \times 5+11 \times 5)$
$=88+2 \times(40+55)$
$=88+190$
$=278 \mathrm{~m}^{2}$