two planes left Seattle at the same time, both traveling due east. One had the rate of 185 mi/h and the other had a rate of 225 mi/hr. After how many hours were they 220 miles apart?

4 answers

d = rate x time
220 = (225-185)*time.
Solve for time.
Check it
185 x time = xx miles
225 x time = yy miles
yy miles - xx miles should = 220.
time?
hour?

i don't get it... help?
come on.
distance = rate x time.
How far will plane one go at 185 mi/hr?
distance = 185 x time.

How far will plane two go at 225 mi/hr?
distance = 225 x time.

Since plane two is traveling at 225 and plane one is traveling at 185, the difference of 40 miles/hour is getting them further apart. The problem asks for how long before that distance is 220 miles. So it is
distance = rate x time
220 = 40 x time
time =- 220/40 = ?? hours. You divide it.

You can check it using miles/hr x time for each plane and subtracting to see if it really is 220 miles.
A train leaves Los Angeles headed for San Diego at 8 a.m. at a constant speed of 50 miles per hour. At the same time, Dagny heads north along the train tracks at 80 miles per hour to stop the train before it gets to Oceanside. Los Angeles and San Diego are 120 miles apart and Oceanside is 50 miles away from Los Angeles. Will Dagney meet the train in time to stop it?