Question
If a sphere with radius 10 cm is painted, but 25% of its surface area is masked and not painted, what is the painted area?
This question was previously asked in
RRB NTPC 2025 Under Graduate CBT 1 Question Paper PDF (20-Jun-2026) (Shift 3)
The correct answer is
300\(\pi\) cm2
Total surface area of the sphere: \(4\pi r^2 = 4\pi\times10^2 = 400\pi\) sq cm.
Painted area (75% of total, since 25% is masked): \(0.75\times400\pi = 300\pi\) sq cm.
Hence, the painted area is \(300\pi\) cm2.
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