Question

in a building there are 24 cylindrical pillars the radius of each will help is 28 cm and height is 4 m find the total cost of painting and covered surface area of all pillars at the rate of
rupees 8 per metre square

Answer 1

There are 24 pillars.

So lets take 1 pillar first,
r= 28cm= 28/100m
h=4m

Curved Surface Area = 2*(22/7)*rh
                                   = 2*(22/7)*(28/100)*4
                                   =176/25
                                   =7.04 m^2

For 24 pillars CSA will be 7.04*24 = 168.96 m^2

 rate = Rs 8.00/m^2
And the cost will be 168.96 *8 = Rs 1351.68

Answer 2

Hieght=4m
Radius = 28cm = 28\100 m
So, surface area of cylindrical pillars
= 2πrh
= 2×22/7×28/100×4
= 7.04 square metre
So, surface area of all pillars
= 24×7.04
= 168.96 square metre
And the total cost of painting
= 168.96×8
= 1351.68 rupees.