Question

the diameter of a roller is 84cm and its length is 120cm. It takes 500 complete revolution to move once to level a play ground. find the areas of the play ground in m squre ​

Answer 1

diameter =84cm

so radius =42cm

=42×10^-2m=0.42m

also l =120cm=1.2m

area of cylinder=2pi r l

= 2×22/7×0.42×1.2

=2×22×0.06×1.2

=44×0.072

=3.168m^2

area covered in 500 rotations =500×3.168=1584m^2

Answer 2

==> D = 84cm

==> R = 84/2 = 42cm

==> L = h = 120cm.

===> C.S.A = 2πrh

===> = 2 × 22/7 × 42 × 120

===> = 2 × 22 × 6 × 120

===> = 31680cm^2

complete revolution = 500

=========> 500 × 31680

Area of playground in cm^2 = 15,840,000cm^2

Find in m^2

1m^2 = 10,000cm^2

( 1m = 100 cm

1m^2 = 100cm × 100cm = 10,000cm^2)

1m^2 = 10,000cm^2

15840000 = 15840000/10000 = 1584m^2