what are t he speeds of the two trains

Question

Train A has a speed of 20 miles per hour greater than that of train B. If train A travels 225 miles in the same time train B travels 165 miles, what are the speeds of the two trains?

Answer 1

OK. It's a simple motion problem, d=rt

 

Train A: 225 = r_A t_A

Train B: 165 = r_B t_B

 

But t_A = t_B = t

and r_A = r_B + 20

 

So 225 = (r_B + 20) t

and 165 = r_B t

 

The difference between those two equations gives 20t = 60, or t = 3 hr.

 

This brings us to r_B = 55 MPH, r_A = 75 MPH. Cheers!