medium   Probability

Radial Measure

A release-checked medium problem for training Uniform, Expected Value/LOTUS, Tail Sum/Integral, Geometric Probability.

Question

A uniformly random point is selected from the interior of the unit circle. Let $R_1$ be the distance of the point to the center, and $R_2$ be the (shortest) distance of the point to the circumference. Find $\ev{\min(R_1,R_2)}$.

Practice focus

This Probability problem is tagged Uniform, Expected Value/LOTUS, Tail Sum/Integral, Geometric Probability. State the random variables and conditioning information explicitly, then check the result against boundary cases before opening hints or a solution.

Explore related collections

Reviewed questions in this area

easyBaby BoyReviewed

Probability · SIG, DE Shaw

easyBad BagelReviewed

Probability · SIG, Jane Street