SOLUTION: Hello, I need help with a uniform motion problem. I have tried different solutions and it is not the answer my book is offering. Problem: A speeding car traveling at 80 mph passe

Question 708476: Hello, I need help with a uniform motion problem. I have tried different solutions and it is not the answer my book is offering.
Problem:
A speeding car traveling at 80 mph passes a police officer. Ten seconds later, the police officer gives chase at a speed of 100 mph. How long, in minutes, does it take the police officer to catch up with the car.
Book Answer:
2/3 of a minute
My work:
Well I use the four box method. So it looks something like this
First time rate * time = distance
Speeding car 80 x+10 80(x+10)
Police Car 100 x 100x
80(x+10)=100x
80x+800=100x
800=20x
40=x Incorrect to the book answer
Second time rate * time = distance
Speeding car 80 x 80x
Police car 100 x-10 100(x-10)
80x=100(x-10)
80x=100x-1000
-20x=-1000
x=50 Incorrect to the book answer
Then calculate for the police car by subtracting 10 gives you 40
This left me thinking if it is to the book answer maybe I need to use .1 instead of 10 because it is 10 seconds not minutes.
Third time rate * time = distance
Speeding car 80 x+.1 80(x+.1)
Police car 100 x 100x
80(x+.1)=100x
80x+8=100x
8=20x
8/20=x Then reduce by 4
2/5=x Again incorrect according to the book answer
So just to try it I flipped it again.
Fourth time rate * time = distance
Speeding car 80 x 80x
Police car 100 x-.1 100(x-.1)
80x=100(x-.1)
80x=100x-10
-20x=-10
x= 10/20
x=1/2 Then substitute 1/2-.1 or 1/2-1/10 = 5/10-1/10=4/10 reduce
x-.1=2/5 still an incorrect answer.
Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!

You wrote:

Speeding car 80 x+10 80(x+10)
Police Car 100 x 100x 
80(x+10)=100x
80x+800=100x
800=20x
40=x Incorrect to the book answer

Which is NOT incorrect to the book answer. Since you wrote

, and the time differential was given as 10 seconds, your unit of measure for

has to be seconds as well.

minute.

John

Egw to Beta kai to Sigma
My calculator said it, I believe it, that settles it

The Out Campaign: Scarlet Letter of Atheism

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