Question

The perimeter of borewell of our village is 440 cm. There is an equally wide stone parapet
around this borewell. If the perimeter of borewell with parapet is 616 cm. Let us write by
calculating that how much width of the stone parapet is.​

Answer 1

Answer:

Given:

Diameter of the well (d) = 140 cm.

Radius of the well (r) = cm = 70 cm

Let the radius of the outer circle (including the stone parapet) be R cm.

Length of the outer edge of the parapet = 616 cm

⇒

⇒

⇒ R = cm = 98 cm

Now, width of the parapet = {Radius of the outer circle (including the stone parapet) - Radius of the well}

= {98 -70} cm = 28 cm

Hence, the width of the parapet is 28 cm.

Answer 2

Perimeter of borewell = 440 cm

Let radius of borewell be r and the radius of borewell with parapet be R

Perimeter of borewell with parapet = 616 cm

Circumference of borewell = 2 π r

440 = 2 * 22/7 * r

440 *7 / 44 = r

r = 7 * 10 = 70 cm

Circumference of borewell with parapet = 2 π R

616 = 2 * 22/7 * R

616 * 7 / 44 = R

R = 14 * 7 = 98 cm

But,

Width of stone parapet = R - r = 98 cm - 70 cm = 28 cm  <= answer