Question

4) A Paper of length and breadth 44cm x 7 cm is rolled along its length to form a cylinder, find the surface area of the cylinder formed.

Answer 1

Since the paper is rolled along its length , the height of the cylinder formed is

the length of the paper and the breadth of the paper is the circumference of the base of the cylinder formed.(Just try to imagine it , or try to take a paper and roll it to check this)

h=44cm

2πr=7cm

Since the cylinder formed is open at both ends, the surface area of the cylinder is

s= 2πr(h)=44×7=308cm²

You can see that it  is actually the area of the sheet itself,because the  cylinder's surface area must be equal to that of the sheet as it is folded from it.