perplexus.info :: Weights and Scales : Three Cups

Three Cups (Posted on 2004-10-25)

You have three cups which differ in volume and shape. You know that the largest cup is less than three times the volume of the smallest cup. Each cup has a mark showing how much one-third is. You also have a drain.

The largest cup is already full of water. Pour water back and forth to fill all three cups to their one-third mark, pouring any excess down the drain.

Note: If a cup is less than one third filled, it may be filled up to the one third line BUT if a cup is over one third full it cannot be poured out to reduce it to exactly one third filled because when the cup is tipped, you have no indicator for one third full when tipped.

Submitted by Brian Smith

Rating: 2.1667 (6 votes)

Solution: (Hide)

Let cup #1 be the largest (currently full) and cup #3 be the smallest.
Pour from #1 into #2 up to the mark in #2.
Pour water from #1 into #3 up to the mark in #3.
Pour all of #3 into #2.
Pour all remaining water from #1 into #3 (discarding any that overflows).
Pour from #3 into #1 up to the mark in #1.
Discard any remaining water in #3.
Pour water from #2 into #3 up to the mark in #3.

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
Puzzle Solution	K Sengupta	2023-04-03 21:45:44
solution	jamie	2005-03-19 17:15:50
solution	jamie	2005-03-19 16:07:12
Another solution	Jeffery	2004-12-01 15:54:15
re(2): Solution	Larry	2004-10-25 20:55:00
re: Solution	nikki	2004-10-25 19:48:03
Solution (probably the same)	nikki	2004-10-25 19:42:34
Solution	Larry	2004-10-25 19:15:29

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