An express and a local train leave Seattle at 3pm and head f

An express and a local train leave Seattle at 3pm and head for Arlington 50 miles away. The express travels twice as fast as the local and arrives 1 hour ahead of the local. Find the speed of the train.

Solution

Let x = speed of the local train
Let 2x = speed of the Express train.
Let t = time taken for the local train to travel.

REQUIRED INFO
Formula: speed = dist/time
distance = 50

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

SOLUTION
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