Let the northbound train's rate be r km/h
Then the westbound train's rate is r+5 km/h
After 2 hours, using d = rt
the northbound train's distance is 2r
the westbound train's distance is 2(r+5)
We use the Pythagorean theorem to write an
expression for their distance apart, which
is the hypotenuse of a right triangle.
distance ap[art =
Make the drawing
Square both sides:
That simplifies to
Which conveniently can be divided through by 8
which is conveniently factorable as
r+20 = 0; r-15 = 0
r = -20; r = 15
Ignore the negative answer.
The northbound train's rate is 15 km/h
The westbound train's rate is 15+5=20 km/h
Edwin