You can put this solution on YOUR website! 2.25 * 600 = x [.25 is one-quarter, which is 15 minutes/60 minutes]
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In words:
In the first hour, the plane traveled 600km
In the second hour, the plane traveled 600km
In 15 minutes, the plane traveled a quarter of that distance: of 600 = 150
Add them together:
600+600+150=???