Kayak Problem

[Dee-M-See]

Two men in Kayaks can paddle at 12mph in calm water
They are on a river flowing at 8mph over its 24 mile length
Man A starts from the mouth of the river
While Man B starts from the top
How many miles from the mouth of the river do they meet?

[Salty]

They need to paddle for an hour to meet (2 x 12 miles). In that hour, the mid-point moves 8 miles towards the mouth, so they meet 4 miles from the mouth.

[factor-fiction]

Excuse my lack of knowledge on geography but does water travel from Top to Mouth?
Anyway, taking account of the current, one travels at 20 mph and the other travels at 4 mph.

Speed = distance/time. So distance = speed x time
Suppose they meet after T hours
After time T, one has travelled 20T, the other 4T.
When they meet the total distance travelled by the pair will be 20 miles (the length of the river).
So 20T+4T=24
24T=24
T=1 hour
After 1 hour the faster kayak travelling at 20 mph has travelled 20 miles; the other, travelling at 4 mph, has travelled 4 miles.

So they meet 20 miles from one end, 4 miles from the other. Probably 4 miles from the mouth.

Oh, same answer as Salty. His explanation seems so much shorter though.

[factor-fiction]

Excuse my lack of knowledge on geography but does water travel from Top to Mouth?
Anyway, taking account of the current, one travels at 20 mph and the other travels at 4 mph.

Speed = distance/time. So distance = speed x time
Suppose they meet after T hours
After time T, one has travelled 20T, the other 4T.
When they meet the total distance travelled by the pair will be 20 miles (the length of the river).
So 20T+4T=24
24T=24
T=1 hour
After 1 hour the faster kayak travelling at 20 mph has travelled 20 miles; the other, travelling at 4 mph, has travelled 4 miles.

So they meet 24 miles from one end, 4 miles from the other. Probably 4 miles from the mouth.

Oh, same answer as Salty. His explanation seems so much shorter though.

[factor-fiction]

Grr, ignore my typos.Basically i agree with Salty

[Dee-M-See]

Thank you for your answers I think 4 miles is the correct answer