Question 29463
<b>DEFINITIONS</b>
Let x = speed of the local train
Let 2x = speed of the Express train.
Let t = time taken for the local train to travel.


<b>REQUIRED INFO</b>
Formula: speed = dist/time
distance = 50


<b>CREATING THE MATHS</b>
For Express train: 2x = 50/(t-1) 
--> t-1 = 50/2x 
--> t = (50/2x) + 1
For Local train: x = 50/t 
--> t = 50/x


<b>SOLUTION</b>
Equate both together for t, giving
(50/2x) + 1 = 50/x
25/x + 1 = 50/x


multiply everything by x... this doesn't change anything, just "scales everything". Reason... to cancel the fractions out.
--> 25 + x = 50
x = 25 mph


and so we have:
Speed of Local train = 25mph
Speed of Express train = 50mph


<b>CHECK</b>
Express train would take 1 hour to travel 50 miles at 50mph.
Local train would take 2 hours to travel 50 miles at 25mph.


jon.