1. Let X be a random variable that represents choosing a multiple of 3 between 1

Question

1. Let X be a random variable that represents choosing a multiple of 3 between 1 and 20 that can be expressed as a sum of two different numbers between 1 and 9 inclusive. Find the expected value of the variable X. Express the answer in two decimals (eg: 10.25)

2. Let X be a random variable that represents choosing a multiple of 3 between 1 and 20 that can be expressed as a sum of two different numbers between 1 and 9 inclusive. Find the variance of the variable X. Express the answer in two decimals (eg: 10.25)

Explanation / Answer

Multiples of 3 between 1 and 20 : 3,6,9,12,15,18

Which can be expressed as sum of two numbers between 1 and 9 are :

3,6,9,12,15

there for value of X = 5.

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