Solution: Represent the arrival times as points $(x, y)$ in a 60-minute square. The condition $ y > x + 15 $ (order matters) corresponds to a triangular region with area $ \frac12 \times (60 - 15)^2 = \frac12 \times 2025 = 1012.5 $. The total area is $ 60^2 = 3600 $. The probability is $ \frac1012.53600 = \frac932 $. - Groen Casting