The probability that the larger of two independent uniform variables on $[0,1]$ is greater than $3/4$ if the smaller one is less than $1/4$

geometric-probabilityprobabilityuniform distribution

Two independent random variables are uniformly distributed on $[0, 1]$.

The question asks if the smaller of the two numbers is strictly less than
$\frac{1}{4}$, then what is the probability that the larger one is strictly greater than $\frac{3}{4}$.

I approached the question with trying to find a suitable area within the unit square. I got two lines that cut off a smaller square of $\frac{1}{4}$ length, hence I calculated the probability as $\frac{1}{16}$; but the answer given is $\frac{2}{7}$ and now I can't understand where I'm wrong.

Best Answer

I used excel to solve the problem :D basic conditional probability problem

Yellow is the requirement (Condition) and Red is the region satisfying the property

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