Multiple choice

A hollow cylinder of height 3 cm,is recasted into a solid cylinder of height 9cm. If the external and internal radii of the hollow cylinder are 4.3 cm and 1.1 cm respectively.What will be the radius of the solid cylinder?

  1. 2.8 cm.

  2. 2.4 cm.

  3. 3.2 cm.

  4. 4.8 cm.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When a shape is recast, its volume remains constant. Volume of hollow cylinder = π(R² - r²)h = π(4.3² - 1.1²) × 3 = π(18.49 - 1.21) × 3 = π × 17.28 × 3. Volume of solid cylinder = πR² × 9. Equating: πR² × 9 = π × 51.84, giving R² = 5.76, so R = 2.4 cm.

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