1.

A water well has a height of 8m and diameter of 3.5m. What is the cost of plastering its curved surface and base at the rate of ₹50/m^2? (Take π = \(\frac{22}{7}\))(a) ₹15000(b) ₹14500(c) ₹14000(d) ₹14700I have been asked this question during an online interview.My question comes from Surface Area of a Right Circular Cylinder topic in chapter Surface Areas and Volumes of Mathematics – Class 9

Answer»

The CORRECT option is (b) ₹14500

Explanation: The total area to be plastered = curved surface area + base area

= 2πrh + πr^2

= \((2 * \frac{22}{7} * 1.75 * 8) + {\frac{22}{7}*(8)^2}\)

= 88 + 201.14

= 289.14 m^2

290 m^2

The cost of PLASTERING area of 1 m^2 = ₹50

Therefore, the cost of plastering area of 290 m^2 = 290 * 50

= ₹14500.



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