SOLUTION: "Suppose two cars are driving in opposite directions. If one car is driving 12 mph more than half of the other car's speed, how fast are the cars traveling (in mph) if it took them

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Question 1050616: "Suppose two cars are driving in opposite directions. If one car is driving 12 mph more than half of the other car's speed, how fast are the cars traveling (in mph) if it took them 72 minutes to to get 96 miles apart"
I have already tried D=rt and plugged in 96=72r but the result was not realistic. I am not sure if I'm using the formula incorrectly or if I am just starting off wrong. Thank you so much!
Answer by ikleyn(52864)   (Show Source): You can put this solution on YOUR website!
.
"Suppose two cars are driving in opposite directions. If one car is driving 12 mph more than half of the other car's speed,
how fast are the cars traveling (in mph) if it took them 72 minutes to to get 96 miles apart"
I have already tried D=rt and plugged in 96=72r but the result was not realistic.
I am not sure if I'm using the formula incorrectly or if I am just starting off wrong. Thank you so much!
~~~~~~~~~~~~~~~~~~~~~~~~~ 


Let "x" be the speed "of the other car", in mph.
Then the speed of the first car is (0.5x + 12) mph.

72 minutes = 60 minutes + 12 minutes =   hour =  hour.

The distance between the cars increases at the rate of (x + (0.5x+12)) = 1.5x + 12 mph.

So your guiding equation is

 = 96.

Simplify. Multiply by 5 both sides.

9x + 72 = 480,

9x = 480 - 72,   

and so on . . . 

Please complete on your own.

There is this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

Among others, there is a section "Word problems" in this textbook, and the topic "Travel and Distance problems" in side of it, specially for you.


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