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What's the time?


This is all about hour glasses. Okay, okay, I know we don't measure time using hour glasses anymore; this is about the period in time when hour glasses were in use.

Once upon a time there was a king. The king enjoyed his food (we all do!). The cook had to be careful that he cooked everything to the king's liking, else he was likely to be punished. The king, of course, did not behead cooks who failed to prepare food to his liking; there would be no cooks willing to cook for him if he went about beheading them. He however punished the cooks in other ways - every time the cooks prepared something that was not to his liking, their wages were deducted (some things never change).

So, here was our cook always on the verge of a nervous breakdown. One day the king asked the cook to boil few eggs. The king was very particular that the eggs should be boiled for exactly nine minutes - not a minute more, not a minute less (of course, a few seconds here and there did not matter). It was strange but true that the king possessed an uncanny sixth sense - just by looking at the eggs he could tell whether they had been boiled for nine minutes. There was no way, therefore, the cook could cheat on him.

The cook had two hour glasses - a big one that could measure seven minutes, and a small one that could measure four minutes. He did not have an hour glass that could measure nine minutes. Can you help the cook measure nine minutes using the seven-minute and four-minute hour glasses. Please do help. The cook has two small children and the cost of education is high. If there is any deduction in his wages, the education of his children would suffer!

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  • Indian Institute of Information Technology, Allahabad (Deemed University) - www.iiita.ac.in
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  • Tata Institute of Social Sciences, Mumbai - www.tiss.edu