I need help with this word problem: 2 trains leave San Francisco at the same time in the same direction. The first train travels 55 mph and the second 68 mph. When will the two trains be 390 miles apart?

**First train:**rate = 55

time = t {they left at the same time}

distance = 55t {distance = rate x time}

__Second train__rate = 68

time = t {they left at the same time}

distance = 68t {distance = rate x time}

At the time they are 390 miles apart, the second train's distance will be equal to the first train's distance plus 390, because the faster second train will end up 390 miles in front of the first train.

68t = 55t + 390 {second train equals first train plus 390}

13t = 390 {subtracted 55t from each side}

t = 30 hours {divided each side by 13}

In

**30 hours**, they will be 390 miles apart.

*- Algebra House*