Question

The diameter of a garden roller is 1.4m and it is 2m long. How much area will it cover in 5 revolutions?

Answer 1

Hint: As we know roller is in shape of cylinder as in figure below:

So we can say in one revolution it will cover an area equal to its curved surface area only.


Complete step by step solution:
Given, height(h) of garden roller is 2m
Diameter(d) of garden roller is 1.4m
Hence radius(r) of garden roller is
$r=\dfrac{d}{2}=\dfrac{1.4}{2}=0.7$
So radius of garden roller is 0.7m
In general curved surface area(S) of cylinder is
$\Rightarrow S=2\pi rh$
On substituting value of r and h
$\Rightarrow S=2\times \dfrac{22}{7}\times 0.7\times 2$
$\Rightarrow S=8.8{{m}^{2}}$
So we can say the area covered in one revolution is $8.8{{m}^{2}}$.
So area(A) covered in 5 revolution is
$\Rightarrow A=8.8\times 5=44{{m}^{2}}$

Note: In general the total surface area(S) of the cylinder is $S=2\pi rh+2\pi {{r}^{2}}$ where r is radius and h is height.
But in this question we only need to consider curved surface area i.e $2\pi rh$.
So we need to take care about calculating the area for one revolution.