Jordan, Jocelyn, Arianna and Isabel have to walk through a long dark tunnel. They only have one torch between them so a maximum of two people can go through the tunnel at any one time. Each person takes a different amount of time to get through the tunnel and if two people walk together they must walk at the rate of the slowest.
Jordan takes 3 minutes, Jocelyn takes 5 minutes, Arianna takes 8 minutes, Isabel takes 9 minutes. What is the least amount of time for all four to walk through the tunnel? 
Notes: 
Example:
If Arianna and Isabel walk through the tunnel together it will take 9
minutes, If Arianna then walks the torch back through the tunnel a total of 17 minutes will have passed. Continue till all four are at the other end of the tunnel.
Topics: Starter  Logic  Problem Solving  Puzzles
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Previous Day  This starter is for 8 February  Next Day
27 minutes:
Jordan and Jocelyn walk through taking 5 minutes
Jordan walks back with the torch taking 3 minutes [8 minutes total]
Arianna and Isabel walk through taking 9 minutes [17 minutes total]
Jocelyn walks back with the torch taking 5 minutes [22 minutes total]
Jordan and Jocelyn walk through taking 5 minutes [27 minutes total]
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