Word problem

Question

two planes took off from Reno. The first plane is traveling 3.5 times as fast as the second plane. After traveling in the same direction for 10 hours they are 2200 miles apart. What is the average speed of each plane? 

Answer 1

Well, Lets call the first plane, plane A and the other, plane B. So plane A is traveling 3.5X, where X is plane B speed. So plane A goes a distance (d=r.t) of 35X miles, while the first one goes a distance of 10X miles. According to the formula for time apart we find that, 10=2200/3.5X-1X, then X=2200/25, then you can solve the problem.