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..

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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..

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..

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

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

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

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.

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!

## 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

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..

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