Pi is irrational, so its decimal expansion never terminates. Keeping a reduced rational coefficient beside π preserves the mathematical value; evaluating it produces a finite approximation for display.

Radius 3 and height 5 give exactly 45π

For V = πr²h, substitution gives π × 3² × 5 = 45π m³. No decimal digit of π is needed to establish that exact result.

Convert the coefficient before evaluating π

VolumeCalc converts the rational coefficient 45 between cubic units and leaves π symbolic. A rounded decimal therefore never becomes the input to another conversion.

Use the decimal for scale, not as a new exact input

The approximation helps compare sizes and communicate a finite number. Its last digit is rounded. Retain the π expression for chained exact work, and remember that physical measurement uncertainty can be larger than the display rounding.