# probability help understanding

*label*Mathematics

*timer*Asked: Jun 6th, 2018

**Question description**

Hi, I need help understanding this 3 questions in more depth. Please provide a detailed explanation.

1) A two step consists in casting a die and then selecting a chip from one of two urns, as

follows: A die is cast and urn I is selected if 5 shows up, otherwise urn II is selected. Urn I contains 3
red chips and 7 white chips, and urn II contains 8 red chips and 2
white chips. Then from the selected urn a chip is drawn at random. What
is the (posterior) probability that urn I has been selected if we know
that a red chip was

drawn?

2) Find the p.d.f.,the mean and the variance of Y=X^2, where X is the random variable, whose p.d.f. is f(x)=c*e^(-x^2/2), x is a real number, and c >0.

3) My telephone rings 13 times each week, the calls being randomly distributed among 7 days. What is

the probability that I get at least one call each day?