Numbers Riddle?

There are four people who need to cross a river. There is only one boat present and it can only hold the maximum of two people at a time and at least one person must man the boat at all times. Meaning, Two people must cross the river, one stays on the other side and the other comes back. The four people are represented by the number of minutes it would take them to cross the river: 1, 2, 5, and 10. When two people go together, it takes the time of the larger number. For instance, If person who takes 1 minute to cross and the person who takes 10 minutes to cross go together, it takes 10 minutes for both of them. There is a time limit of 17 minutes to get all four people across, in what order do the people travel to get all four across in 17 minutes or less?

Update:

Remember to add the time of the person coming back as well...

Example:

If 1 and 10 go one way.. its 10 minutes. but then 1 must come back.. adding it to 11 minutes.

14 Answers

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  • 1 decade ago
    Favorite Answer

    1 and 2 cross, 1 returns (3 min)

    5 and 10 cross, 2 returns (3 + 12 = 15 min)

    1 and 2 cross (15 + 2 = 17 min)

  • 1 decade ago

    Best answers:

    1 and 10 = 10

    1 and 2 = 2

    1 and 5 = 5

    2 and 5 = 5

    2 and 1 = 2

    2 and 10 = 10

    Weird answers:

    10 and 2 = 10

    5 and 1 = 5

    2 and 1 = 2

    2 and 10 = 10

    5 and 1 = 5

    2 and 5 = 7

  • 1 decade ago

    Well like you said if 2 go together like 1 and 10 the largest number is the minutes it takes 4 the 2 of them.So 1 & 2 cross it takes 2 minutes. 2 & 5 cross it takes 5 minutes so far its taken them 7 minutes then 5 & 10 cross it takes them 10 minutes!!! So it takes them alltogether 17 minutes!

    Thanx 4 the riddle that was great ill read all of ur riddles for now on because they're great Thanx alot!!!

  • 1 decade ago

    As long as the person that takes 1 min to cross goes every crossing you will be at 17 min. Example:1+2 go1st time= 2min, 1+5 go 2nd=5min,1+10 go 3rd= 10min. now 10+5+2=17min.

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  • 1 decade ago

    there is no way it takes 19 min to get across. 10 first with 1 , 1 comes back gets 5 so thats 16 mins so far goes back to get 2 but on his way back it hits 17mins so it would take 19 for all four to cross.

  • 1 decade ago

    1 with 2,

    1 with 5,

    1 with 10

  • 1 decade ago

    okay...

    1 and 10 -----------------------------> 10 minutes (10)

    <----------------------------1 goes back

    1 and 5 --------------------------------> 5 minutes (5)

    <----------------------------- 1 goes back

    1 and 2 ----------------------------------> 2 minutes (2)

    you get 17, but if each person is represented by a number which is how many minutes it takes them to cross, either way..... you would really get 19!!!!

  • 1 decade ago

    1st round: 1 & 2 go... then 1 comes back...2mins

    2nd round:1&10 go... then 1 come back...10mins

    3rd round: 1&5 go.....5 mins...

    total is 17 mins....

  • Ohhhhh dang. I'm feeling a head-ache trying to figure that out. I'm sooooo bad with numbers. I better just give up.

  • 1 decade ago

    never mind some one else posted it

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