SOLUTION: I found a very similar problem to this one but when I went through all the steps the answer came out negative and Im pretty sure you cant have a negative speed? Alvin paddled for

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Question 149180: I found a very similar problem to this one but when I went through all the steps the answer came out negative and Im pretty sure you cant have a negative speed?
Alvin paddled for 4 hours with a 6km/h current to reach a campsite. The return trip against the current took 10 hours. Find the speed of Alvin's canoe in still water.

Found 2 solutions by edjones, josmiceli:
Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
st=d, s=speed in still water, t=time, d=distance
4(s+6)=d
10(s-6)=d
4(s+6)=10(s-6)
4s+24=10s-60
84=6s
s=14 km/h in still water.
.
Ed

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let s = the speed of Alvin's canoe
Let d = the length of the trip
Going with the current:
d+=+%28s+%2B+6%29%2At
t+=+4 hrs is given
d+=+%28s+%2B+6%29%2A4 km
Going against the current:
d+=+%28s+-+6%29%2A10 km
Make the 2 expressions for d equal to each other
%28s+%2B+6%29%2A4+=+%28s+-+6%29%2A10
4s+%2B+24+=+10s+-+60
6s+=+84
s+=+14
The speed of the boat in still water is 14 km/hr
check:
d+=+%28s+%2B+6%29%2A4
d+=+%2814+%2B+6%29%2A4
d+=+80 km
and
d+=+%28s+-+6%29%2A10
d+=+%2814+-+6%29%2A10
d+=+80 km
OK