Denis wrote:
A[U@u].........................k..........................[V@v,W@w]B
Straight path AB, length k.
U (speed = u) is at A, V (speed = v) and W (speed = w) are at B.
All leave at same time.
U meets V at point C, picks up V, turns around, heads towards A, drops V
off at point D, turns around and heads towards B; V continues towards A.
U meets W at point E, picks up W, turns around, heads towards A:
they arrive at A at same time as V.
When V and W were "aboard" U, speed was u.
No loss of time at pick-ups and turn-arounds!
BC = a, AD = b and BE = c.
What is k in terms of a,b,c ?
Assuming D is between A and B?