Question

The diameter of a roller is 84cm and its length is 120cm. It takes 500 complete revolutions to move once over to level a playground. The area of the playground in m^2 is
A) 1584
B) 1284
C) 1384
D) 1184​

Answer 1

Answer:

A)1584

Step-by-step explanation:

d=84cm

r=42cm=>0.42m

and,h=120cm=>1.20m

NOW,

CSA OF ROLLER =2πrh

=>2×22/7×0.42×1.20

=3.168 m^2

THEREFORE,IN 500 Revolutions = 3.168×500

=>1584m^2

Answer 2

${\bold{\underline{\underline{Answer:}}}}$

${\bold{\therefore Area\:of\:ground=1584\:m^{2}}}$

${\bold{\underline{\underline{Step-by-step\:explanation:}}}}$

$\underline \bold{Given : } \\ \implies Diameter = 84 \: cm \\ \\ \implies length= 120 \: cm \\ \\ \implies Revolution = 500 \: complete \\ \\ \underline \bold{To \: Find: } \\ \implies Area \: of \: playground = ?$

• According to given question :

$\bold{Radius=\frac{84}{2}=42\:cm}\\\\\bold{Using \: C.S.A \: of \: cylinder : } \\ \implies C.S.A \: of \: cylinder = 2\pi rh \\ \\ \implies C.S.A = 2 \times \frac{22}{7} \times 42 \times 120 \\ \\ \implies C.S.A= 2 \times 22 \times 6 \times 120 \\ \\ \bold{\implies C.S.A=31680 \: cm^{2} } \\ \\ \bold{For \: Area \: of \: ground : } \\ \\ \implies Area \: of \: ground = 500 \times 31680 \\ \\ \implies Area = 15840000 \: {cm}^{2} \\ \\ \implies Area = \frac{15840000}{10000} \\ \\ \bold{ \implies Area \: of \: ground = 1584 \: {m}^{2} }$