The triangle on the left side has two legs of length 4 m and 6 m. It's a right triangle, so the hypotenuse has length √((4 m)² + (6 m)²) = 2√13 m. Only the 4 m leg and the hypotenuse count towards the shape's overall perimeter.
The rectangular part contributes 9 m from the top side and 9 m from the bottom one, thus a total of 18 m.
The half-circle has diameter 6 m (indicated by the dashed line, same as the height of the triangle on the left). A full circle with diameter <em>d</em> has circumference <em>πd </em>; a half-circle with the same diameter would then contirubte <em>πd</em>/2, or in this case, 3<em>π</em> m.
So, the total perimeter of the shape is
(4 m + 2√13 m) + 18 m + 3<em>π</em> m ≈ 38.6 m
