Father Time has an hourglass. Every minute, the bottom chamber collects twice as many grains as the minute before. If it takes 60 minutes to fill completely, at what minute was the hourglass exactly half full?
59 minutes
Since the amount doubles every minute, whatever amount is in the glass at minute 59 will double in the next minute (minute 60) to fill it completely. Therefore, it was half full at minute 59.
About this riddle
Math riddles hide a calculation inside a short story. Pull out the numbers, work out what is being asked, and watch for a trick such as a unit change.
Difficulty: Medium. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
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