Train station...

Question

Two trains leave the station at the same time, one heading east and the other west. The eastbound train travels at
85 miles per hour. The westbound train travels at 105 miles per hour. How long will it take for the two trains to be 342 miles apart?

Answer 1

Okay so we want to know when their distance will = 342 and we know that d = r * t (distance = rate * time)

 

 (This is all the setup and logic required to set up the final equation from the base d = r*t because sometimes it's nice to know how things come together, otherwise skip to "and we know...")

 

r1 = 85; r2 = 105

so

d1 = r1 * t1 and

d2 = r2 * t2

t1 = t2(they left at the same time) so we'll call t1 = t2 = t

 

and we know d1+d2 equals 342(their distance apart = 342) so lets solve that:

r1*t+ r2*t = 342

85*t + 105*t = 342

190*t = 342

t = 342/190 hours

 

Answer 2

85x + 105x = 342

 

190x = 342

 

x = 342/190

85(342/190) + 105(342/190) = 342

 

Hope that helps