MHB Efficient Family Bridge Crossing Strategy

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To efficiently get the family across the bridge in under 30 seconds, the optimal strategy involves careful pairing and returning with the lamp. First, the two fastest members, the boy and his brother, cross together, taking 3 seconds. The boy then returns with the lamp, adding 1 second, totaling 4 seconds. Next, the father and mother cross together, taking 8 seconds, and the brother returns with the lamp, adding another 3 seconds, bringing the total to 15 seconds. Finally, the boy and grandpa cross together, taking 12 seconds, resulting in a total crossing time of 27 seconds, successfully getting everyone across within the time limit.
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5 members of a family are to cross the bridge and the bridge can hold only 2 at a time.Its also dark so they have a lamp...They have to do the crossing in less than 30 seconds...
It takes 1 second for the boy to cross the bridge,3 seconds for his fatty brother,6 seconds for their father,8 seconds for the boys' mother and 12 seconds for their grandpa...
When two of the family are crossing together it takes the time of the slowest person to cross the bridge...(Thats obvious)
How will you get all them across?
 
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Looks like nobody wants it.Ok,here is the answer

Denis said:
http://www.mymathforum.com/viewtopic.php?f=38&t=39218#p160599

a:1, b:3, c:6, d:8, e:12[

return trip #1: a+b, a returns : time = 4
return trip #2: d+e, b returns : time = 15
return trip #3: a+c, a returns : time = 7
final 1 way trip: a+b : time = 3

Total time = 4+15+7+3 = 29



Edit:No matter what I do I can't edit this my way...
 
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