Question

A circle has a radius of 7 cm. What is the nature of its circumference?

• A. Rational
• B. Irrational
• C. Whole number
• D. Integer

Answer 1

The correct option is B

Irrational

$2\pi r$ is the formula for the calculation of circumference. It is irrational as $\pi$ is irrational unless radius is the exact reciprocal of $\pi$.
For r = 7 cm,
$2\pi r=2\pi \times 7=14\pi$
Thus, the value of circumference $14\pi$ for a circle with radius 7 cm is irrational.