Question

A rectangular piece of paper of dimensions 20cm×14cm is rolled along the breadth to form a cylinder. Find the radius of the base of the cylinder so formed.

Answer 1

the circumference of the base is 20cm
we know, the circumference of the cylinder = 2×22/7×r
20=44/7×r
20×7/44 = r
3.18 = r
hence, radius of the cylinder is 3.18cm

Answer 2

Given:

Length of rectangular piece of paper,l=20 cm

Breadth of rectangular piece of paper,b=14 cm

To find:

Radius of the base of the cylinder

Solution:

Circumference of base of cylinder=20 cm

$2\pi r=20$

We know that

$\pi=\frac{22}{7}$

$2\times \frac{22}{7}\times r=20$

$r=\frac{20\times 7}{2\times 22}$

$r=\frac{35}{11} cm$

Hence, the radius of base of the cylinder=35/11 cm