RRB NTPC Mains or Stage 2 Model Paper 9 with solutions

Question : 34 of 120

Marks: +1, -0

A well 22.5 deep and of diameter 7 m has to be dug out. Find the cost of plastering its inner curved surface at ₹3 per sq. metre.

Solution:

(b) Area of the inner curved surface of the well dug

= [2π × 3.5 × 22.5] = 2 22 /7×3.5 ≥×22.5

= 44 × 0.5 × 22.5 = 495

sq. m.
∴ Total cost = 495 × 3 = ₹1485

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