Question

the diameter of a 120cm long roller is 84cm. it takes 1000 complete revolution moving once over

Answer 1

Radius of the roller (r) = 84/ 2 cm = 42 cm 
Length of the roller (h) = 120 cm 
Curved surface area of the roller = 2πrh 
= 2 × 22/ 7 × 42 × 120 cm2 = 44 × 720 cm2= 31680 cm2 

∴ area covered by the roller in 1 revolution = 31680 cm2 

∴ area covered by the roller in 1000 revolutions = 31680 × 1000 cm2 = 31680000 cm

Answer 2

here you can radius = 84/ 2 cm = 42 cm & roller=120 or, area of the roller = 2πrh 

= 2 × 22/ 7 × 42 × 120 cm2 = 44 × 720 cm2= 31680 cm2 

∴ area covered by the roller in 1 revolution = 31680 cm2 

∴ area covered by the roller in 500 revolutions = 31680 × 500 cm2 = 15840000 cm

therefore area = 15840000/ 100× 100 m2 = 1584 m2 Ans.