Question

14) Find the number of metallic circular disc with 1.5 cm base diameter and one of height 0.2 cm to be melted to form a right circular cylinder of height 10 cm and diameter 4.5 cm.

Answer 1

Each one of those metallic disk is also a cylinder (just a very very short one), and its volume is
V = πr²h = π(.75)²(.2) = 9π/80 cm³
The right circular cylinder has volume V = π(2.25)²(10) = 405π/8 cm³.

Divide the larger cylinder's volume by the volume of each metallic disk = (405π/8) / (9π/80) = 450 coins