# Thread: Need to cross a bridge...

1. ## Need to cross a bridge...

Another homework problem...

Andrea, Bill and Charlotte need to cross a bridge as quickly as possible.
Andrea can walk across in 10 minutes, Bill walks it in 5 minutes and Charlotte walks it in 2 minutes. There is also a bicycle available which can thake any one person across the bridge in one minute. It cannot take more than one person at a time.

Explain how it is possible for the trioto cross the bridge in 3 minutes or less. Give distances [fractions of the length of the bridge] and/or times travelled on foot and on bicycle for each person.

- A correct distance for one person to ride the bicycle
- A correct distance for another to ride the bicycle
- A correct description of how it is done.

Thankyou for reading and hope you can help.

2. Originally Posted by Bartimaeus
Another homework problem...

Andrea, Bill and Charlotte need to cross a bridge as quickly as possible.
Andrea can walk across in 10 minutes, Bill walks it in 5 minutes and Charlotte walks it in 2 minutes. There is also a bicycle available which can thake any one person across the bridge in one minute. It cannot take more than one person at a time.

Explain how it is possible for the trioto cross the bridge in 3 minutes or less. Give distances [fractions of the length of the bridge] and/or times travelled on foot and on bicycle for each person.

- A correct distance for one person to ride the bicycle
- A correct distance for another to ride the bicycle
- A correct description of how it is done.

Thankyou for reading and hope you can help.
A starts out on the bicycle, and B and C start walking.

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
out.

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.

RonL

3. Thankyou.