Question 810798
Direction_________speed____________time_________________distance
upriver___________r-5______________(___)________________15
downriver_________r+5______________(___)________________15
Total________________________________4



The way Rate*Time=Distance works, know that Time=Distance/Rate:


Direction_________speed____________time_________________distance
upriver___________r-5______________{{{15/(r-5)}}}________________15
downriver_________r+5______________{{{15/(r+5)}}}________________15
Total________________________________4


Solve for r in {{{highlight(15(1/(r-5)+1/(r+5))=4)}}}