# Solution to the [[Squares and a Semi-Circle]] Puzzle +-- {.image} [[SquaresandaSemiCircle.png:pic]] > Some squares and a semicircle. What’s the perimeter of the combined shape? =-- ## Solution by [[circumference|Circumference of a Circle]] The diameter of the circle is $2$, so the [[circumference]] of the [[semi-circle]] is $\frac{1}{2} \pi \times 2 = \pi$. There are seven squares along the bottom, so each individual square has side length $\frac{2}{7}$ and the perimeter of the lower region is $(2 + 7 + 2) \times \frac{2}{7} = \frac{22}{7}$. This is one of the classic [[approximations for pi]]. The total perimeter of the combined shape is therefore: $$ \pi + \frac{22}{7} \simeq 2\pi $$