What was the Air Force plane's speed?

Question

An Air Force plane left Nairobi 3.8 hours before a cargo plane. The planes flew in opposite directions. The cargo plane flew 314 km/h for 7.1 hours. After this time the planes were 5728.3 km apart.

Answer 1

The cargo plane flew a distance of, d_c= (314)(7.1) =2229.4 km.

The Air Force plane flew for a total time of, t = 3.8+ 7.1= 10.9h (the time the air force plane flew prior to the cargo plane, 3.8h, added to the time both airplanes were flying, 7.1h) and a total distance of, d_af =  5728.3 - 2229.4 =3498.9 km in the opposite direction. Since the airplanes flew in opposite direction, we subtract to find the result. In this case the difference is the distance that the air force plane, d_af , flew.

 

So now to calculate the speed of the air force plane

V_af = 3498.9/10.9= 321 km/h