Help solve my word problem!

Question

Alvin paddled for 5 hours with a 5-km/h current to reach a campsite. The return trip against the same current took 10 hours. What is the speed of the boat in the still water?

Answer 1

Usong d=rt

 

the he rates differ by the current the times differ as stated. But the distance is the same. 

D=(r+5km/hr)•5hr

=(r-5km/hr)10hr

 

Solving for r 

 

(r•hr +5km)
=(2r•hr -10km)

15km=r•hr

r=15km/hr

 

Check 

 

D=100km using either equation