Which fraction is a common approximation to pi?

• A. 3/1
• B. 18/7
• C. 22/7
• D. 7/22

Answer: (C)

Using a simple fraction to approximate pi.

The idea here is to pick a fraction that closely matches the ratio of a circle’s circumference to its diameter. Among common, easy-to-use fractions, 22/7 is very close to π. In decimals, 22/7 is about 3.142857, while π is about 3.141593, so the difference is only around 0.00126. That small gap makes 22/7 a handy, widely used approximation for quick calculations.

The other options don’t line up well with π: 3/1 equals 3, which underestimates π by about 0.1416; 18/7 is about 2.5714, far from π; and 7/22 is about 0.318, the reciprocal of 22/7 and not a close representation of π.