12.4 Spheres and Hemispheres

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Key Formulas

Solved Examples

Step 1

  1. Identify Surface: Tin-plating is done on the inside. So we need Inner CSA.

Step 2

  1. Dimensions: Diameter d=10.5d = 10.5, Radius r=5.25r = 5.25 cm.

Step 3

  1. Calculate CSA: 2πr2=2×227×5.25×5.252\pi r^2 = 2 \times \frac{22}{7} \times 5.25 \times 5.25.

Step 4

  1. Solve: 44×0.75×5.25=173.2544 \times 0.75 \times 5.25 = 173.25 cm².

Step 5

  1. Cost: Rate is ₹16 per 100 cm². Cost = 173.25100×16=1.7325×16=27.72\frac{173.25}{100} \times 16 = 1.7325 \times 16 = 27.72.
Final Answer

₹27.72

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