Two planes leave an airport at 2 pm one flying south at 450

Two planes leave an airport at 2 pm, one flying south at 450 km/hr, the other flying north at 675 km/hr. At what time will they be 3600 km apart?

They are separating at a speed of (450+675) = 1125 km/hr
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Equation:
time = distance/rate
time = 3600/1125 = 3.2 hr = 3 hr and 12 minutes
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The time will be 2pm + 3hr and 12 min = 5:12 pm