The slope of the airplane's ascent is calculated using the rise over run formula and is 3 / 8 or 0.375.
Step-by-step explanation:
The slope of the airplane's ascent can be calculated by the ratio of the rise over the run. In this case, the airplane climbs 15 feet up (rise) for every 40 feet it moves forward (run). Therefore, using the formula slope = rise / run, we can determine that the slope of the airplane's ascent is 15 / 40, which simplifies to 3 / 8 or 0.375.