how long before they are 45 miles apart?

Question

two trains leave a station traveling in the same direction on parallel track. on train is traveling at 72 mph and the other is traveling at 66 mph. how long before they are 45 miles apart?

Answer 1

Hi Rachel,

 

Recall d = rt

Distance = rate times time

 

let

d₁ = distance the first train travels

r₁ = the speed of the 1st train = 72 mph

d₂ = distance the second train travels
r₂ = the speed of the 2nd train = 66 mph

t = time travelled (in hours)

 

We want to know when the two trains are 45 miles apart

d₁+d₂ = 45

 

r₁t + r₂t = 45

72t + 66t = 45

138t = 45

t = .326 hours