Question

A rectangular piece of paper measuring 25cm by 21cm is rolled along its breadth to form a cylinder. Find the total surface area of the cylinder so formed.

Answer 1

if the paper is rolled then circumference of the top of cylinder is 25 cm and its height is 21 cm.
circumference=2* 22/7* radius
25=44/7r
25/44*7=r
175/44=r
tsa of cylinder=2*22/7*175/44(21+175/44)
175/7(924/44+175/44)
175/7*1099/44
175*157/44
27475/44cm sq. units

Answer 2

by rolling the paper circumference of the top of cylinder is 25 cm and its height is 21 cm.
therefore circumference=2x 22/7x radius
25=44/7r
25/44 x 7=r
175/44=r
tsa of cylinder=2 x 22/7 x 175/44(21+175/44)
175/7(924/44+175/44)
175/7 x 1099/44
175 x 157/44
27475/44cm sq. units
=624.43