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The Two Ropes Burning Riddle — A 45-Minute Interview Brain Teaser
You have two ropes each burning in exactly 1 hour with non-uniform burn rate. How do you measure exactly 45 minutes? What do you do the moment you light rope one?
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What is the answer to the two ropes 45 minutes riddle?
Light rope 1 from both ends and rope 2 from one end at the same time. Rope 1 burns out in 30 minutes; at that instant light rope 2's other end, and it burns out in 15 more minutes for a total of exactly 45 minutes.
Why does lighting a rope from both ends measure 30 minutes?
A rope that takes 1 hour to burn from one end will burn in half the time, 30 minutes, when lit from both ends, even though the burn rate is uneven, because the two flames always meet at the halfway point in burn time.
Is the two ropes riddle a real interview question?
Yes. This classic timing puzzle is a popular logic and brain-teaser question used in tech and quant interviews to test lateral thinking.