Question

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?

Answer 1

Here, r = 3 cm, h = 10.5 cm 

The penholders have only one base i.e., these are open at one end. 

Total surface area of 1 penholder 

= 2πrh + πr2 = πr (2h + r) 

= 22 /7 × 3 (2 × 10.5 + 3) cm² 

= 22/ 7 × 3 × 24 cm² 

Total surface area of 35 penholders = 22/ 7 × 3 × 24 × 35 cm² = 7920 cm² 

Hence, 7920 cm2 of cardboard is needed Ans.