What is the radius of the circular plate of thickness 1 cm made by melting a…

2023

What is the radius of the circular plate of thickness 1 cm made by melting a sphere of radius 3 cm?

  1. A.

    6 cm

  2. B.

    5 cm

  3. C.

    4 cm

  4. D.

    7 cm

Attempted by 5 students.

Show answer & explanation

Correct answer: A

Step 1: Compute the sphere's volume. Volume of sphere = (4/3)πr^3 = (4/3)π·3^3 = (4/3)π·27 = 36π cubic cm.

Step 2: Express the plate's volume. The plate is a cylinder of thickness 1 cm, so Volume of plate = π·R^2·h with h = 1 cm, hence π·R^2·1 = π·R^2.

Step 3: Equate volumes and solve for R.

  • π·R^2 = 36π

  • R^2 = 36 ⇒ R = 6 cm

Answer: 6 cm.

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