Question

A circle of radius $0.39$ is circumscribed about a square. What is the approximate perimeter of the square?

• A. 78
• B. 1.21
• C. 1.78
• D. 2.21
• E. 2.78

Answer 1

The correct option is D 2.21

Let the side length of square be $a$
We have $\sqrt{2}a=2r=0.78$ $\Rightarrow a=0.78/\sqrt{2}$
Perimeter of square is $4a=1.56\sqrt{2}=2.21$