Question

a well of a diameter 150 cm has a 30 cm wide parapet running around it .find the area of parapet



please solve this problem

Answer 1

Answer : 16971.428 cm^2.


Explanation -

Given :

Diameter = 150 cm

The radius = d/2 = 150/2 = 75cm

Given width = 30 cm

Outer radius of the parapet = R = 75 + 30 = 105 cm


Finding the area :-

The area of the parapet =


= $\pi( {R}^{2} - {r}^{2} )$


= $\pi( {105}^{2} - {75}^{2} )$


= $\dfrac{22}{7} (11025 - 5625)$


= $\dfrac{22}{7} \times 5400$


= ${16971.428 \: cm}^{2}$

Answer 2

=Area of big circle - area of small circle
=22/7 × 75×75 - 22/7 × 105 × 105
=22/7 × 5625 - 22/7 × 11025
=123750/7 - 242550/7
=118800/7
=16971.42