SOLUTION: Two cars are leaving their driveways at the same time heading for school that is 15 miles away. One car drives at 40 mph, while the other driving at 50 mph. How long has the second

Algebra ->  Rate-of-work-word-problems -> SOLUTION: Two cars are leaving their driveways at the same time heading for school that is 15 miles away. One car drives at 40 mph, while the other driving at 50 mph. How long has the second      Log On


   

Question 793383: Two cars are leaving their driveways at the same time heading for school that is 15 miles away. One car drives at 40 mph, while the other driving at 50 mph. How long has the second car been at school when the first car arrives?
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
CAR_____________speed_____________time________________distance
Slow____________40________________(___)_______________15
Fast____________50_______________(___)________________15

Fill in the missing time quantities of each car using r%2Ah=d, where h is for time in hours. We have a formula from this, h=d%2Fr.

CAR_____________speed_____________time________________distance
Slow____________40________________(15/40)_______________15
Fast____________50_______________(15/50)________________15

The fast car spent less time driving to arrive at school. Upon his arrival, the slow car is still traveling, and the fast car then waits 15/40-15/50 hour for the slow car to arrive.

15%2F40-15%2F50
%285%2F5%29%2815%2F40%29-%284%2F4%29%2815%2F50%29
%285%2A15%2F200-4%2A15%2F200%29
%2875-60%29%2F200
15%2F200
Divide by %285%2F5%29,

3%2F40

%283%2F4%29%2F10

0.75%2F10

highlight%280.075%29 hours

A better unit is as MINUTES:
0.075%2A60=highlight%284.5%29 minutes