SURFACE AREAS

AND VOLUMES

• Sum based on Cuboid

Q. A fish tank is in the form of a cuboid whose external measures are

80 cm × 40 cm × 30 cm. The base, side faces and back face are to be

covered with a coloured paper. Find the area of the paper needed.

Sol.

= 80

× 40

= 3200 cm²

Area of two side faces =

= 2

× 40

× 30

= 2400 cm²

Area of back face

= 80

× 30

= 2400 cm²

l

b

h

l

lb

bh

bh

lh

= l × b

= l × h

For cuboid fish tank,

length (l ) = 80 cm

breadth (b) = 40 cm

height (h) = 30 cm

Area of base

Area of the paper needed =

Area of base +

Area of two side faces +

Area of back face

What is the formula to find area of base ?

What is the formula to find area of a side face ?

What is the formula to find area of back face ?

2 × b × h

∴ Area of the paper needed is 8000 cm².

Area of the paper needed

= 3200

+ 2400

+ 2400

= 8000 cm²

Q. A fish tank is in the form of a cuboid whose external measures are

80 cm × 40 cm × 30 cm. The base, side faces and back face are to be

covered with a coloured paper. Find the area of the paper needed.

Area of the paper needed =

Area of base +

Area of two side faces +

Area of back face

l

b

h

= Area of base

+ Area of two side faces

+ Area of back face

Sol.