Question

There are 20 cylindrical pillars in a building, each having a diameter of 50 cm and height 4m . Find the cost of cleaning them at Rs. 14 per m^2 .​

Answer 1

Answer:

Rs. 1760

AIM:-

To Find The Curved Surface Area Of All The Cylinders and Then The Cost To Clean Them.

Why Curved Surface Area And Not Total Surface Area?

That is because the top circular face of the pillar would be attached to the ceiling and the bottom one would be attached to the ground. The only part left to clean is the Curved surface area.

INFORMATION:-

No. of Pillars= 20

Radius of each pillar = 25 cm = ¹/₄ meters

Cost of Cleaning = Rs. 14/ m²

Height = 4 mtrs.

CALCULATION:-

● C.S.A of one cylinder = 2(pi)×radius×height

= 2 × ²²/₇ × ¹/₄ × 4

= ⁴⁴/₇ m²

●Therefore, C.S.A of 20 pillars = 20×⁴⁴/₇

☆WE KEEP THE C.S.A AS IT IS BECAUSE 7 IN THE DENOMINATOR WILL GET CANCELED WITH THE 14 WE MULTIPLY IN THE NEXT STEP.

● Now the cost to clean 20 pillars = 14×(Total area to be cleaned)

=> Cost = 14 ×20×⁴⁴/₇

= 2×20×44

= Rs. 1760