694.444s

1.all 3 carry and reach the end at the same time.
2. C is carrying 3 times from the start point and drop 2 times at point A in the midle, finish carrying one times. B carry from starting point and drop stuff at point B; go back to A to pick 2 times, drop one at B and carry one time to the end. 3. A finish carrying 3 times, one from start point, 2 from point B. 4. everyone finish a one way 1000 with their top speeds. evertone make round trips with their average speed.

T=1000/2+4(1000-b)/1.5=1000/4+4(b-a)/3=1000/6+4a/4.5

a=1187.5
b=1854.166667
T=694.4444444

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• correction -passenger101- ♂ (31 bytes) () 10/15/2008 postreply 06:53:58