Question

I cannot figure out what the answer to this problem is. Can somebody help plz? any help is greatly appreciated!

Tony swims 100 m downstream in 175 seconds. It takes him 400 seconds to swim back upstream.

5. Find Tony's rate with the current. I got r+c=175, where r=Tony's rate and c=rate of current.

6. Find Tony's rate against the current. I got r-c=400.

7. Find Tony's rate with no current.

8. Find the rate of the current.

9. What are the total distance and total time?

10. Find Tony's average speed.

Ok, I tried the addition method thing where you add r+c=175 to r-c=400 and you get 2r=575 which equals r=287.5, but it isn't possible. Can somebody help? I might be able to figure out problems 8.-10., but I don't get problem 7. Oh, and one more question...what would be the units for his average speed? Would it be meters/seconds?

Thank you very very very much!

try doing what tonyt did and count the time it takes

uh... what do you mean by that?

make a chart and it becomes very easy

-------------Dist------Rate-----Time

upstream---400(r+c)m---r+c m/s---400 sec
downstream-175(r-c)m---r-c m/s---175 sec

but we know the distance is 100 m, so...

400(r+c)=100
175(r-c)=100

r+c=1/4 I divided by 100
r-c= 4/7 I divided by 175

add these two
2r=23/28
r=23/56 m/s or .411 m/s

sub back to get c=.161 m/s