Question

A roller of dia. 14 cm and length 7 cm is rolled along a flat ground. Calculate the area covered when the roller makes 25 revolutions

Answer 1

Given :

• Diameter of Roller is 14 cm .
• Length/Height of Roller = 7 cm .

To Find :

• Area covered by roller in 25 revolutions .

Solution :

Firstly we will find Area covered by 1 revolution .

$\longmapsto\tt{Radius=\dfrac{14}{2}=7\:cm}$

Using Formula :

$\longmapsto\tt\boxed{C.S.A\:of\:Cylinder=2\pi{rh}}$

Putting Values :

$\longmapsto\tt{2\times\dfrac{22}{{\not{7}}}\times{{\not{7}}}\times{7}}$

$\longmapsto\tt{44\times{7}}$

$\longmapsto\tt\bf{308\:{cm}^{2}}$

Now ,

Area covered in 25 revolutions :

$\longmapsto\tt{308\times{25}}$

$\longmapsto\tt\bf{7700\:{cm}^{2}}$

So , The Area covered in 25 revolutions is 7700 cm² .

___________________

• C.S.A of Cylinder = 2πrh
• T.S.A of Cylinder = 2πr(r+h)
• Volume of Cylinder = πr²h

___________________

Answer 2

Answer:

${ \huge { \pmb{ \bf {Given}}}}$

• Diameter of roller = 14 cm
• Length of roller = 7 cm
• Revolution made = 25

$\huge \pmb{ \bf{To \: Find}}$

Area covered

${ \huge{ \pmb{ \bf{Solution}}}}$

At first we need to find Radius of roller

Radius = Diameter/2

Radius = 14/2

Radius = 7 cm

We know that

${ \large { \pmb{ \bf{CSA = 2\pi rh}}}}$

CSA = 2 × 22/7 × 7 × 7

CSA = 44/7 × 49

CSA = 44 × 7

CSA = 308 cm²

Finding area covered

${ \large{ \bf{ \pmb{ Area \: covered = Revolution \times CSA}}}}$

Area covered = 25 × 308

Area covered = 7700 cm²