Answer:
The elevation of the airplane decreases by 9 km.
Step-by-step explanation:
We use the distance-rate-time formula: d = rt.
Here, the rate is r = 0.15 km/min and the time is t = 60 min. Simply plug these into the formula:
d = rt
d = 0.15 * 60 = 9 km
So, the change in elevation in the last 60 minutes is 9 km. However, note that the rate is negative (-0.15 km/min), which means that the elevation actually is decreasing.
Thus, the answer is: the elevation of the airplane decreases by 9 km.
<em>~ an aesthetics lover</em>