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Four members of a band are walking to a night
concert. They decide to take a shortcut, but must cross a bridge. Luckily
they have one flashlight. Because of the varying size of their instruments,
it takes each member a different amount of time to cross the bridge
- it takes the first person one minute, the second person two minutes,
the third person five minutes and the fourth person ten minutes. They
must cross the bridge in pairs, travelling at the slower speed so if
the one minute person went with the ten minute person, it would take
a total of ten minutes. Since there is only one flashlight, one person
must come back across the bridge, then another pair can cross. They
only have 17 minutes to cross the bridge and still get to the concert
on time.
First, the one minute person and the two minute
person must cross the bridge, for a total of two minutes. Then the one
minute person should come back with flashlight - total of three minutes.
The five minute person and the ten minute person cross together next,
making the total thirteen minutes. Now the two minute person goes back
and (total now fifteen minutes) and gets the one minute person and they
cross together bringing the total to seventeen minutes. |
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