The students of a Vidyalaya were asked to participate in a competition for making and decorating penholders in the shape of a cylinder with a base, using cardboard. Each penholder was to be of radius 3 cm and height 10.5 cm. The Vidyalaya was to supply the competitors with cardboard. If there were 35 competitors, how much cardboard was required to be bought for the competition?

`["Assume "pi=22/7]`

#### Solution

Radius (*r*) of the circular end of cylindrical penholder = 3 cm

Height (*h*) of penholder = 10.5 cm

Surface area of 1 penholder = CSA of penholder + Area of base of penholder

= 2π*rh* + π*r*^{2}

`=[2xx22/7xx3xx10.5+22/7xx(3)^2]cm^2`

`=(132xx1.5+198/7)cm^2`

`=(198+198/7)cm^2`

`=1584/7cm^2`

`"Area of cardboard sheet used by 1 competitor "=1584/7cm^2`

Area of cardboard sheet used by 35 competitors

`=(1584/7xx35)cm^2=7920cm^2`

Therefore, 7920 cm^{2} cardboard sheet will be bought.