A cylinder (r = 6 cm, h = 12 cm) is bored through by a hole (r = 3 cm, full height). What percentage of the original volume is removed?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 25%.
Volume of big cylinder = πr2h = π × 62 × 12 = 432π cm2
Volume of hole = π × 32 × 12 = 108π cm2
Percentage removed = (108π/432π) × 100 = 25%