Four persons can cross a bridge in 3,7,13,17 minutes. Only two can cross at a time. find the minimum time taken by the four to cross the bridge.

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Answered by: Stelone B R

  • Nov 4th, 2007


Send the 17 and 3 first.. After 3 min, send 7, after 10 minutes send 13... So within 17 min 3 persons crossed..They were 3,7 and 17 and the remaining person will cross the bridge in 6 another minutes.. Therefore total and minimum time required is 17+6=23 minutes..

Showing Answers 1 - 24 of 24 Answers

Stelone B R

  • Nov 4th, 2007
 

Send the 17 and 3 first.. After 3 min, send 7, after 10 minutes send 13... So within 17 min 3 persons crossed..They were 3,7 and 17 and the remaining person will cross the bridge in 6 another minutes.. Therefore total and minimum time required is 17+6=23 minutes..

velkanesh

  • Nov 8th, 2009
 

Ans: 20 minutes

   First send 17 and 7. After 7 minutes, 7 is at finish and 17 needs 10 more minutes to complete his travel. now send 13. After 10 minutes 17 reaches finish and 13 needs 3 more minutes to complete. now send 3. both 3 and 13 reach destination at the same time after 3 minutes. hence the time taken is 7+10+3=20 minutes..

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vinodhani

  • Nov 25th, 2009
 

First 17 and 7 going so that 7 will reach in 7 min remain 10
Now 13 and 17 is going so that  17 I will reach in 10 min remain 3
Now 13 and 3 is going so that both reached in 3 min. so totall min to reach is 7+10+3=20

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sachinkiit

  • Feb 7th, 2010
 

Sequence ie 17,3=3min

                        17,7=7min
                     17,13=13min
-----------------------------------------
                      Total=23 mins

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They can cross in 20 minutes. First 17 and 7 can go after 7 minutes 13 can go mean while in 17 mins first 17 crosses then 3 will go.

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sravan547

  • Oct 1st, 2010
 

13 and 17 at a time so max time is 17minutes
3 and 7 at a time so max time is 7 by adding these two we get the 17+7=24
so the minimum time taken by four persons is 24minutes

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vinodhini

  • Oct 1st, 2012
 

first send d[17min] and c[13]min.. c finishes in 13min that time d left with 4min. so send b[7min].. at 17th min d finishes so send a[3].. so answer is 20min not 23 min

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SUBHANKAR ARMAN

  • Oct 9th, 2012
 

At first persons with 17m and 13m start. When 13m finish, 7m starts. There are remaining 4 minutes when 17m and 7m are walking together. After 4 minutes 17m finish and 7m is still walking for 3min. But during these 3minutes 3m starts and is walking with 7m. They finish in 3 minutes both. So there is total 17+3 minutes=20 minutes.

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kuldeep

  • Dec 20th, 2012
 

at 0th minute, send 3,7.
at 3rd minute, send 17.
at 7th minute, send 13.

at 20th minute, all sent!

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Blaidd

  • Jun 17th, 2015
 

3 carries 17: 3 minutes
7 carries 13: 7 minutes
Only 2 cross at any one time and all 4 get across in 10 minutes

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