Troy was trying to catch up with the rest of his group, who had left earlier on a kayaking trip. Troy paddled 8 hours downstream, covering 72 miles before realizing that he had passed his group’s campground. He had to paddle back upstream for 18 miles to get back to his group’s campground. If the trip back upstream took Troy 6 hours, how fast was the river flowing (in mph)?
A. 2 mph
B. 3 mph
C. 6 mph
D. 9 mph

Question

Troy was trying to catch up with the rest of his group, who had left earlier on a kayaking trip. Troy paddled 8 hours downstream, covering 72 miles before realizing that he had passed his group’s campground. He had to paddle back upstream for 18 miles to get back to his group’s campground. If the trip back upstream took Troy 6 hours, how fast was the river flowing (in mph)?
A. 2 mph
B. 3 mph
C. 6 mph
D. 9 mph

nikato · Answer

so let b=speed of boat
c= speed of surrent

b+c= downstream
b-c=upstream

nikato · Answer

set up 2 equations

8(b+c)=72
6(b-c)=18

nikato · Answer

so divide both sides by 8 in the first equation
and divide both sides by 6 in the second equaiton

anonymous · Answer

divide?

nikato · Answer

yes

anonymous · Answer

im confused would you mind showing me?

nikato · Answer

sure

nikato · Answer

|dw:1389507976492:dw|does this make sense?