Question
Sphere A has a radius of 6 cm and Sphere B has a radius of 3 cm. What is the ratio of the surface area of A to that of B?
This question was previously asked in
RRB NTPC 2025 Graduate CBT 2 Question Paper PDF (10-Jul-2026) (Shift 1)
The correct answer is
\(4:1\)
The surface area of a sphere is \(4\pi r^{2}\), so it is proportional to the square of the radius.
The ratio of surface areas is \(\frac{r_A^{2}}{r_B^{2}} = \left(\frac{6}{3}\right)^{2} = 2^{2} = 4\).
So the ratio of surface area of A to B is \(4:1\).
Hence, the required ratio is \(4:1\).
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