



 
Hi Keith, The perimeter of a semicircle is made up of two parts, a diameter and a curved piece which has the length of half the circumference of the circle. Suppose the diameter is $d$ units long then you know that the circumference of the circle is $\pi d$ units. Thus the perimeter of the semicircle is $d + \frac{\pi}{2} d$ units. But you know that the perimeter is 37 units so \[d + \frac{\pi}{2} d = 37.\] Solve for $d.$ Write back if you need further assistance,  


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