Question
A solid cylinder of radius 35 cm and height 50 cm is melted and recast into smaller identical cylinders, each having radius 3.5 cm and height 15 cm. How many complete such smaller cylinders are formed?
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RRB NTPC 2025 Under Graduate CBT 1 Question Paper PDF (20-Jun-2026) (Shift 3)
The correct answer is
333
Number of small cylinders equals the ratio of volumes, since volume is conserved on melting and recasting.
Volume of a cylinder \(V=\pi r^{2}h\).
Large cylinder: \(V_1=\pi(35)^{2}(50)=\pi\times 1225\times 50=61250\pi\) cm3.
Small cylinder: \(V_2=\pi(3.5)^{2}(15)=\pi\times 12.25\times 15=183.75\pi\) cm3.
Number of small cylinders \(=\dfrac{V_1}{V_2}=\dfrac{61250\pi}{183.75\pi}=\dfrac{61250}{183.75}=333.33\ldots\)
Only whole small cylinders count, so 333 complete small cylinders are formed.
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