Question 960442
<i>Two cars leave towns d kilometers apart at the same time and travel toward each other. One car's rate is k kilometers per hour more than the others. If they meet in t hours, what is the rate of the faster car?</i>


________________speeds________time_________distance
FAST____________r+k____________t____________(____)
SLOW_____________r_____________t____________(____)
Total_______________________________________d


________________speeds________time_________distance
FAST____________r+k____________t____________(r+k)t
SLOW_____________r_____________t____________rt
Total_______________________________________d


{{{(r+k)t+rt=d}}}

{{{rt+kt+rt=d}}}

{{{2rt+kt=d}}}

{{{2rt=d-kt}}}

{{{highlight(r=(d-kt)/(2t))}}}


Question means, what is r+k ?

{{{highlight(r+k=(d-kt)/(2t)+k)}}}
Use the given values d=640, k=18, t=4;
and evaluate the right member of this solution formula.


r+k=89