Question

Find the cost of painting the curved surface of a cylinder of base diameter 35 cm and height 20 cm at the rate of 20 paise per cm2.​

Answer 1

Answer :

›»› The cost of painting the curved surface area of a cylinder is Rs.440.

Given :

• Diameter of a cylinder = 35 cm.
• Height of a cylinder = 20 cm.
• The rate of 20 paise per cm².

To Find :

• The cost of painting the curved surface area of a cylinder.

Solution :

Firstly we will find the radius of a cylinder.

As we know that

→ Radius = Diameter ÷ 2

→ Radius = 35 ÷ 2

→ Radius = 17.5

The radius of a cylinder is 17.5 cm.

Now,

As we know that

→ CSA of cylinder = 2πrh

→ CSA of cylinder = 2 * 22/7 * 17.5 * 20

→ CSA of cylinder = 2 * 22 * 2.5 * 20

→ CSA of cylinder = 44 * 2.5 * 20

→ CSA of cylinder = 110 * 20

→ CSA of cylinder = 2200

The curved surface area of cylinder is 2200 cm².

Now, Cost of painting = Curved surface area of cylinder * 20

→ Cost of painting = 2200 * 20

→ Cost of painting = 44000

Now, converting the cost of painting from paise to rupees.

→ Cost in rupees = 44000 paise * 1 rupees/100 paise

→ Cost in rupees = 44000 * 1/100

→ Cost in rupees = 44000/100

→ Cost in rupees = 440/1

→ Cost in rupees = 440

Hence, the cost of painting the curved surface area of a cylinder is Rs.440 .

Answer 2

Answer:

$\huge \bf \: Given$

• Diameter of curved surface cylinder = 35 cm
• Height of curved surface cylinder = 20 cm
• Rate of painting per cm = 20 paise

$\huge \bf \: To \: do$

Total cost of painting

$\huge \bf \: Solution$

Firstly we have to find radius of cylinder.

$\huge \sf\: radius = \frac{diameter}{2}$

$\sf \leadsto \: r \: = \dfrac{35}{2}$

$\sf \leadsto \: r \: = 17.5 \: cm$

Therefore Radius of Cylinder = 17.5 cm

Now,

Finding CSA of cylinder

$\huge \bf \: CSA \: = 2\pi rh$

$\sf \leadsto \: csa \: = 2 \times \dfrac{22}{7} \times 17.5 \times 20$

$\sf \leadsto \: csa \: = 2 \times 22 \times 2.5 \times 20$

$\sf \leadsto \:csa \: = 44 \times 50$

$\sf \leadsto csa \: = 2200$

Now,

Cost of painting = Curved surface area × 20

$\sf \leadsto \: cost \: of \: painting \: = 2200 \times 20$

$\huge \sf \leadsto \: cost \: = 44000 \: paise$

Now,

We will convert paise to rupees

$\sf \leadsto \:cost \: (rupees) = 44000 \times \dfrac{1}{100}$

$\sf \leadsto \: cost \: (rupees) = \dfrac{44000 \times 1}{100}$

$\sf \leadsto \: cost \: (rupees) = 440$