SOLUTION: this is a yes or no question.....
A car travels a 1-mile track at an average speed of 15 mph. Is it possible for the car to travel the next mile so that the average speed for th
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Question 934569: this is a yes or no question.....
A car travels a 1-mile track at an average speed of 15 mph. Is it possible for the car to travel the next mile so that the average speed for the 2 mi is 30 mph?
thanks so much for the help!!
Found 3 solutions by josmiceli, jim_thompson5910, DrBeeee:
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Average speed is always: ( total distance ) / ( total time )
The time for the 1st mile is: hrs
Let = the time for the 2nd mile in hrs
-----------------
You need to solve:
------------
It is impossible, since the car can't travel the 2nd
mile in zero time
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
A similar problem was asked/answered here
http://www.algebra.com/algebra/homework/word/travel/Travel_Word_Problems.faq.question.160404.html
The conclusion is that it is impossible to do so (the solver explains why). Let me know if that helps or not. Thanks.
Answer by DrBeeee(684) (Show Source): You can put this solution on YOUR website!
Answer: No
Why, you ask?
Let's figure it out.
Let d = rt, with rate r in mph and t in hrs, then d is miles.
The time to travel the first mile is
(1) t1 = d/r or
(2) t1 = 1/15
Let the rate for the second mile be x, then the time for the second mile is
(3) t2 = 1/x
The average speed (rate) for the two miles is
(4) rave = d/t or
(5) rave = 2/(t1+t2) or
(6) rave = 2/(1/15 + 1/x)
We are asked if rave can be 30mph. Let's see. Can (6) be equal to 30?
(7) 30 = 2/(1/15 + 1/x) or
(8) 30 = 2/(x + 15)/(15x) or
(9) 30 = 30x/(x + 15) or
(10) 1 = x/(x + 15) or
(11) (x + 15) = x or
(12) 15 = 0
I don't recall that 15 = 0, do you?
So it is impossible. You need to travel the second mile in zero time. then we have in (5)
(13) rave = 2/(t1+t2) or
(14) rave = 2/(1/15+0) or
(15) rave = 2/(1/15) or
(16) rave = 30
It means that we travel at an infinite rate to take zero seconds!
You're welcome.
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