
Step-by-step explanation:
arc MK = 90°
arc JMK = 180°
arc MK + arc JM = 180° (sum of arc in a semicircle)
90 + arc JM = 180
arc JM = 180 - 90
arc JM = 90°
To get the length of an arc, we will apply the formula:

diameter = JK = 16.4 miles
diameter = 2(radius)
radius = diameter/2
radius = 16.4/2 = 8.2 miles
π = 3.14
Substitute the values:

