# Two planes

Two planes flying from airports A and B, 420 km distant against each other. Plane from A took off 15 minutes later and flies at an average speed of 40 km/h higher than the plane from B. Determine the average speed of this two aircraft if you know that it will meet 30 minutes after takeoff A.

Result

a =  360 km/h
b =  320 km/h

#### Solution:

a=b+40
a*30/60 + b* (45/60)=420

a-b = 40
30a+45b = 25200

a = 360
b = 320

Calculated by our linear equations calculator.

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