SarkariPYQ

SSC CGL 2023 PYQ — Question 71

SSC CGL - 27 July 2023 - Shift 1 • Quantitative Aptitude • Q71

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A hemispherical bowl has a radius of 7 cm. It is to be painted from inside as well as outside. Find the cost of painting it at the rate of Rs.40 per 20 cm2 ? (Take thickness of the bowl as negligible).

Show answer & explanation

Correct answer: A

Explanation

The correct answer is option 1 i.e. Rs. 1,232.

Curved surface area of hemisphere = 2πr22 \pi r^2

Area of inner hemisphere = 2×227×722 \times {22 \over 7} \times 7^2 = 308 cm2

Area of outer hemisphere = 2×227×722 \times {22 \over 7} \times 7^2 = 308 cm2

Accordibng to the given question,

Total area of the inner and outer hemisphere = 308 + 308 = 616 cm2

Cost of painting = 61620616 \over 20 × 40 = 1232

Hence the cost of painting the hemisphere is Rs.1,232.