Question 696634: I can paddle a canoe upstream at 2 mph and downstream at 6 mph. How far upstream can I go if I want to return in exactly 4 hours?
Using D=R*T, I came up with 2x + 6(4 - x)=4 where x=hours traveling upstream; so x=5 hours (leads to wrong answer: 10 miles upstream, 9 miles downstream)
Using logic, I can see that the answer is 6 miles upstream (3 hours upstream, 1 hour back down.), but I can't figure out the right equation to get that. I think that the left portion of equation is correct, but not the 4 on the right.
(I am trying to relearn algebra and how to apply it 52 years after first having the class.)
Answer by MathTherapy(10555)   (Show Source):
You can put this solution on YOUR website! I can paddle a canoe upstream at 2 mph and downstream at 6 mph. How far upstream can I go if I want to return in exactly 4 hours?
Using D=R*T, I came up with 2x + 6(4 - x)=4 where x=hours traveling upstream; so x=5 hours (leads to wrong answer: 10 miles upstream, 9 miles downstream)
Using logic, I can see that the answer is 6 miles upstream (3 hours upstream, 1 hour back down.), but I can't figure out the right equation to get that. I think that the left portion of equation is correct, but not the 4 on the right.
(I am trying to relearn algebra and how to apply it 52 years after first having the class.)
Let distance to travel upstream be D
Then distance to travel downstream also = D
Speed upstream (against current): 2 mph
Speed downstream (with current): 6 mph
Time to travel upstream, plus time to travel downstream equals total allotted time. From this, a time-equation can be formed, as follows:
3D + D = 24 ----- Multiplying by LCD, 6
4D = 24
D, or distance that one can travel each way (upstream as well as downstream) in 4 hours at the given rates of speed =  , or  miles
You can do the check!!
Send comments and “thank-yous” to “D” at MathMadEzy@aol.com
|
|
|
