# Two ropes and 45 mins [duplicate]

You have got two ropes of same mass, same material, same thickness and same length but mass is not uniformly distributed over the length. Both of the ropes burn in 1 hour but you cannot cut them in half and expect the two halves to burn in 30 minutes because of non-uniform distribution.

How would you measure 45 minutes using these two ropes?

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What is the probability that at any given instant (second), the sum of the length burnt by both ropes will be equal to the original length of either rope?

• @IAmInPLS I edited the question. Please look over it Dec 7, 2016 at 8:08

Since everything burns in 45 minutes = 2700 seconds and if we consider the second the un-divisible unit of time, the sum of the burned lengths can be equal to the original length of each rope only in 1 second out of the 2700 and it's not equal for the rest of them. So the probability is $\frac{1}{2700} = 0.037 \%$ which is kind of slim.