SOLUTION: Hello I'm having trouble setting this problem up. Any help would be appreciated. Thanks. A traveler having 18 miles to go, calculates that his usual rate would make him one-half

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Question 1201248: Hello I'm having trouble setting this problem up. Any help would be appreciated. Thanks.
A traveler having 18 miles to go, calculates that his usual rate would make
him one-half hour late for an appointment; he finds that in order to arrive on
time he must travel at a rate one-half mile an hour faster. What is his usual
rate?

Found 3 solutions by ikleyn, josgarithmetic, MathTherapy:
Answer by ikleyn(52800)   (Show Source): You can put this solution on YOUR website!
.
Hello I'm having trouble setting this problem up. Any help would be appreciated. Thanks.
A traveler having 18 miles to go, calculates that his usual rate would make
him one-half hour late for an appointment; he finds that in order to arrive on
time he must travel at a rate one-half mile an hour faster. What is his usual rate?
~~~~~~~~~~~~

Let x be his usual rate, in miles per hour.


The time to travel 18 miles at his usual rate is    hours.


The time to travel with the faster rate, (x+0.5) miles per hour, is   hours.


The longer time is   of an hour longer:

     -  =   of an hour.    (1)


    +----------------------------------------------+
    |    At this point, the setup is complete:     |
    |    you just have an equation to solve.       |
    +----------------------------------------------+


To solve it, multiply both sides by 2x*(x+0.5) = 2x^2 + x.  You will get

    36(x+0.5) - 36x = x^2 + 0.5x

    36x + 18 - 36x = x^2 + 0.5x

    x^2 + 0.5x - 18 = 0

     =  =  = .


Obviously, only positive root fits  x =  =  = 4  miles per hour.


Check it, by substituting into equation (1)

     = 4.5 - 4 = 0.5 =   of an hour.   ! correct !


ANSWER.  The usual rate is 4 miles per hour.

Solved.



Answer by josgarithmetic(39620)   (Show Source): You can put this solution on YOUR website!
Using the description

            SPEED        TIME          DIST.

USUAL       r            18/r            18

FASTER      r+1/2       18/(r+1/2)       18 

DIFFERENCE                1/2

---------simplify and solve.







discrim,


Answer by MathTherapy(10552)   (Show Source): You can put this solution on YOUR website!
Hello I'm having trouble setting this problem up. Any help would be appreciated. Thanks.
 A traveler having 18 miles to go, calculates that his usual rate would make
him one-half hour late for an appointment; he finds that in order to arrive on
time he must travel at a rate one-half mile an hour faster. What is his usual
rate?

Let usual/regular speed be S
Then time taken to get to appointment = 
Increasing speed by , or .5 mph means that his new speed to get there on-time is: (S + .5) mph.
So, time he'd take to get to the appointment, based on his new speed = 
At the new speed , he'll get there on-time by "shaving" , or .5 hour off of the previous late-time, or 
We then get the following TIME equation: 
                                           ------ Multiplying by LCD, 
                                    
                                      ----- Multiplying by 4
                                 (S - 4)(2S + 9) = 0 ----- Factoring trinomial
                                  S - 4 = 0            or      2S + 9 = 0
           Normal/Usual speed, or S = 4 mph       or      2S = - 9 (ignore)

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