Half moon lagoon has a diameter of 85 yards. What is the lagoon’s perimeter?

1. Find the circumference of the full circle:

C = \pi \times d = \pi \times 85

2. Find the circumference of the half circle:

C_{\text{half}} = \frac{\pi \times 85}{2}

3. Since it's a half circle, add the diameter to the half circumference to get the full perimeter:

P = \frac{\pi \times 85}{2} + 85

4. Calculate the perimeter:

P=133.518+85=218.518\,\text{yards}

5. The perimeter of the lagoon is:

218.518\,\text{yards}