# The Inner Diameter of a Well is 4.20 Metre and Its Depth is 10 Metre. Find the Inner Surface Area of the Well. Find the Cost of Plastering It from Inside at the Rate Rs.52 per Sq.M. - Geometry

Sum

The inner diameter of a well is 4.20 metre and its depth is 10 metre. Find the inner surface area of the well. Find the cost of plastering it from inside at the rate Rs.52 per sq.m.

#### Solution

Inner radius of the well, r = 4.2/2= 2.1 m
Depth of the well, h = 10 m
∴ Inner surface area of the well = 2πrh = 2 x 22/7 x 2.1 x 10 = 132 m2

Rate of plastering = Rs 52/m2
∴ Cost of plastering the well from inside
= Inner surface area of the well × Rate of plastering
= 132 × 52
= Rs 6,864

Thus, the inner surface area of the well is 132 m2 and the cost of plastering the well from inside is Rs 6,864.

Concept: Surface Area of a Cuboid
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#### APPEARS IN

Balbharati Mathematics 2 Geometry 9th Standard Maharashtra State Board
Chapter 9 Surface Area and Volume
Problem Set 9 | Q 8 | Page 123
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