A cone of radius 9 cm and height 15 cm is melted and made into a cylinder of height 45 cm. The diameter of the cylinder is:

Correct option is D

Given:
Cone radius = 9 cm
Cone height = 15 cm
Cylinder height = 45 cm
Formula Used:
Volume of a cone = $$\frac{1}{3}\pi r^2h$$​​
The volume of a cylinder = πr²h
Solution:
The volume of the cone is equal to the volume of the cylinder.

​$$\frac{1}{3}\pi r^2h = \pi r^2 h \\\frac{1}{3} (9^2 \times 15) = (r^2 \times 45) \\r^2 = 9 \\r = 3$$

The diameter of the cylinder is twice the radius.

Diameter = 2r = 2× 3 = 6 cm

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