Question

EXERCISE - 10.2
1. A closed cylindrical tank of height 1.4 m. and radius of the base is 56 cm.
is made up of a thick metal sheet. How much metal sheet is required (Express
in square meters)
3
2. The volume of a cylinder is 308 cm.. Its height is 8 cm. Find its lateral surface area
and total surface area.
3. A metal cuboid of dimension 22 cm. x 15 cm. x 7.5 cm. was melted and cast into a​

Answer 1

1.

Given, radius of the base of a cylinder r = 56cm = 0.56m

And height h = 1.4m

To find the metal sheet required, we need to find the total surface area of the cylinder.

Total surface area of the

cylinder = 2πr(r + h)

= 2 × π × 0.56 × (0.56 + 1.4)

= 6.89 ≃ 6.9m2

2.

Answer.

THEREFORE, LATERAL SURFACE AREA OF CYLINDER = 2πrh

= 2×22/7×154×8

= 7,744cm

3.

Given a metal cuboid of dimension length 22 cm breadth 15 cm and height is 7.5 cm

Then volume of cuboid =22×15×7.5=2475cm

3

If we melt this cuboid and cast in the cylinder of height 14cm

Then the volume of cuboid =volume of cylinder

Let r is a radius of a cylinder

Then volume of cylinder =πr

2

h=

7

22

×r

2

×14

∴

7

22

×r

2

×14=2475

⇒r

2

=

22×14

2475×7

=56.25

⇒r=7.5cm