Question

A cylindrical stool has a base of diameter 70 cm and height 25 cm find the cost of painting 50 such stools if the cost per m sq is rs 55.

Answer 1

`Cost = Rs.3630`

Explanation:

Given

`d = 70cm` --- Diameter

`h = 25cm` --- Height

`Cost = Rs.55`

`Cylinders = 50`

First, we calculate the surface area of 1 cylinder

This is calculated as:

`SA=2\pi r(r + h)`

The radius is calculated as:

`r =(1)/(2)d`

`r =(1)/(2)*70`

`r = 35`

The expression becomes:

`SA=2 * (22)/(7) * 35(35 + 25)`

`SA=2 * (22)/(7) * 35 * 60`

`SA=2 * 22 * 5 * 60`

`SA=13200cm^2`

Convert to
`m^2`

`SA=(13200m^2)/(10000)`

`SA=1.32\ m^2`

The surface area of 50 of such is:

`Total = 50 * 1.32m^2`

`Total = 66m^2`

The cost is then calculated as:

`Cost = 66 * Rs.55`

`Cost = Rs.3630`