Question

Car A leaves San Diego at noon driving at 60 mph along a route which is 400 miles long to San Francisco. Car B leaves San Francisco 2 hours later traveling along the same route at 80 mph. How far from the midpoint of the route are they when they meet? Are they closer to San Diego?
This is my question and I don't get what I'm supposed to do.. I don't know when they meet I'm not sure where to put the variables either.

Answer 1

Distance = speed x time
Distance travelled by car A when car B started = 60 x 2 = 120 miles
Number of miles remaining at the time car B started = 400 - 120 = 280 miles.

At time of their meeting both cars has travelled a combined distance of 280 miles and has spent the same time.
Let t be the time they travelled together before they meet, then the sum of the distance travelled by car A and car B is 280miles.
60t + 80t = 280
140t = 280
t = 280/140 = 2 hours

After 2 hours car A has travelled a further 60 x 2 = 120 miles and car B has travelled 80 x 2 = 160 miles.

Total distance travelled be car A is 120 + 120 = 240 miles

Midpoint of the journey = 400/2 = 200 miles
Therefre, at the time they met, the were 40 miles from the midpoint and they are close to San Francisco.