The solution would be like this for this specific problem:
  
 Area of Circle = 16(π)
 = 16 * 3.14
 = 50.24
 
 Area of Square = 64
 = 64 – 50.24
 = 13.76
  
 Area of Square but not on the circular board = 13.76 / 64
 = 0.215
 Percentage value = 0.215 * 100%
 = 21.5%
 So, to the nearest percent, the probability that the dart lands inside the square but not on the circular dartboard is 21.5%.