A starts out on the bicycle, and B and C start walking.Originally Posted by Bartimaeus
A drops the bicycle when he 7/9-th of the way across, and walks from
there, arriving (if I have done the sums correctly) 3 minutes after starting
C walks 7/9-th of the way, picks up the bicycle and rides back to 4/9-th
of the distance across the bridge, then walks the rest of the way across
the bridge, arriving 3 minutes after starting.
B walks until they pick up the bicycle 4/9-th of the way across the
bridge, and arrive at of before 3 minutes after starting.
I leave the remaining detail to you to fill in.
Diagram is in attachment.