(Image credit: Flickr usser Christina B Castro)
Neatorama presents our collaboration with Pzzlr, a site where you can always find a riddle to exercise your brain. Can you solve this one?
Louise has invited some very important business associates over for dinner and is cooking a soufflé. The soufflé requires exactly 29 minutes in the oven in order to be perfectly cooked. As her guests are sipping cocktails Louise remembers that the oven timer is broken, her watch is at the jewellers being repaired and her only other clock fell off the wall the day before and smashed to pieces (why do things always happen in threes!).
Too embarrassed to ask her guests for help, Louise remembers that she has two hourglasses in the cupboard. The first times exactly 13 minutes and the second exactly 21 minutes.
How can Louise cook her soufflé using only the two hourglasses for timing?
Can you figure this out? The answer is at Pzzlr!
Look for a new puzzle here at Neatorama every Wednesday, and check out Pzzlr for a puzzle anytime!
2. after 13 mins turn the 13er again and let it run the remaining 8 mins till the 21er is through.
3. the 13er has now 5 mins left. so turn it now again, because it now runs for another 8 mins wich equals to 29.
1.) 29-21 = 8
2.) 21-13 = 8
3.) an hourglass can be inverted before its time is up, in order to double the time it just recorded.