# Time Trial Puzzle

749.0K Views

If you have an 11 minute and 13 minute hourglass, how can you accurately time 15 minutes?

leonard0_da_vinci Guru Asked on 11th August 2015 in

Start both hourglasses then when the 11 minute hourglass has finished immediately flip it again. When the 13 minute hourglass runs out the 11 minute hourglass will have 9 minutes left, so flip it and it will last another 2 minutes, 13 minutes + 2 minutes = 15 minutes.

leonard0_da_vinci Guru Answered on 11th August 2015.

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