Question

Q1.The diameter of a cylinder is 28 cm and its height is 20 cm. Find its total surface area.​

Answer 1

Explanation:

Given:

A cylinder with -

Diameter = 28 cm

Height = 20 cm

What To Find:

We have to find -

The total surface area.

Formula Needed:

$\bf \mapsto TSA = 2 \pi r^2 + 2 \pi rh$

Where -

TSA = Total surface area.

R = radius

H = Height

Solution:

Finding the radius.

We know that -

$\sf \mapsto R = \dfrac{Diameter}{2}</p><p>$

Substitute the value,

$\sf \mapsto R = \dfrac{28}{2}$

Divide 28 by 2,

$\sf \mapsto R = 14 \: cm$

Finding the TSA.

Using the formula,

$\sf \mapsto TSA = 2 \pi r^2 + 2 \pi rh$

Substitute the values,

$\sf \mapsto TSA = 2 \times \dfrac{22}{7} \times 14 \times 14 + 2 \times \dfrac{22}{7} \times 14 \times 20$

Multiply 14 with 14,

$\sf \mapsto TSA = 2 \times \dfrac{22}{7} \times 196 + 2 \times \dfrac{22}{7} \times 14 \times 20$

Multiply 14 with 20,

$\sf \mapsto TSA = 2 \times \dfrac{22}{7} \times 196 + 2 \times \dfrac{22}{7} \times 280$

Cancel 7 and 196,

$\sf \mapsto TSA = 2 \times 22 \times 28 + 2 \times \dfrac{22}{7} \times 280$

Cancel 7 and 280,

$\sf \mapsto TSA = 2 \times 22 \times 28 + 2 \times 22 \times 40$

Multiply 2, 22, and 28,

$\sf \mapsto TSA = 1232 + 2 \times 22 \times 40</p><p>$

Multiply 2, 22, and 40,

$\sf \mapsto TSA = 1232 + 1760$

Add 1232 and 1760,

$\sf \mapsto TSA = 2992 \: cm^2</p><p>$

Final Answer:

∴ Thus, the total surface area of the cylinder is 2992 cm².

Answer 2

Answer:

Total surface Area,

r = d/2 = 14cm h = 20 cm

A = 2πr(h+r)

= 2(3.14)(14(14+20)

= 2(3.14)(14)(34)

= 2989.28cm²