SOLUTION: two cars leave manila and travel in opposite directions. one of the cars averages 12 km/h less than the other. After 3 hours, they are 396 km apart. What is the average speed of ea

Question 247657: two cars leave manila and travel in opposite directions. one of the cars averages 12 km/h less than the other. After 3 hours, they are 396 km apart. What is the average speed of each car?
Answer by oberobic(2304) (Show Source): You can put this solution on YOUR website!
You always have to start with the equations that are given and add what you know. For example, we know d = r*t, where d=distance, r=rate, and t=time
.
x = speed of car 1
y = speed of car 2, which = x-12 (given)
.
t = 3 for both cars
.
a = distance driven by car 1 = x * 3 = 3x
b = distance driven by car 2 = (x-12) * 3 = 3x-36
.
a+b = 396
.
Substituting,
3x + 3x-36 = 396
6x = 432
x = 72
.
y = x-12 = 60
.
Checking to see if they cover 396 miles combined in 3 hrs...
3*72 = 216
3*60 = 180
OK.
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