Question

Find the surface area (in cm. sq.) of a container with radius 4 cm and height 10 cm, assuming it

has an open top. The bottom is closed.

A) 301.6

B) 351.9

C) 251.3

D) 421.6​

Answer 1

Answer:

Given: Radius=4cm

Height=10cm

Total surface area=2πr(h+r)sq.units

=2×

7

22

×4(10+4)

351.85sq.cm

Answer 2

Given :

Radius of cylinder = 4cm

Height = 10cm

To find : Surface area of the cylinder with open top and closed bottom

We know that,

Curved surface area = 2πrh

[Curved surface area refers to the area of the figure excluding the top and bottom]

Hence Surface area of a cylinder with open top and closed bottom will be :

Curved surface area + Area of base

Curved surface area:

$2 \times \dfrac{22}{7} \times 4 \times 10$

$= \dfrac{1760}{7} {cm}^{2}$

Area of base :

In a cylinder the base is made of a circle.

Therefore area of base = πr²

$\dfrac{22}{7} \times 4 \times 4$

$= \dfrac{352}{7} {cm}^{2}$

Adding both the areas,

$\dfrac{1760 + 352}{7}$

$= \dfrac{2112}{7} {cm}^{2}$

Hence final answer =≥ 301.6 cm² (approx)

Note :

Why is the shape referred a cylinder?

In any 3d shape we have learnt, we need 3 measurements to find the area : Length, breadth and height. Only in a few shapes like the cylinder, sphere, cone and hemisphere, 2 measurements are required.Therefore we can conclude that the shape must be a cylinder.