10 good reasons why lying can b helpful
Answer: 30 miles
Step-by-step explanation:
45/6 = 7.5 miles per minute
7.5 x 4 = 30 miles per minute
Should be 21 boys because 7+7+7 equal 21 and 3+3+3 equal 9 which equals 30
For any distribution, the sum of the probabilities of all possible outcomes must be 1. In this case, we have to have

We're told that
, and we're given other probabilities, so we have

The expected number of calls would be
![E[X]=\displaystyle\sum_xx\,P(X=x)](https://tex.z-dn.net/?f=E%5BX%5D%3D%5Cdisplaystyle%5Csum_xx%5C%2CP%28X%3Dx%29)
![E[X]=0\,P(X=0)+1\,P(X=1)+\cdots+4\,P(X=4)](https://tex.z-dn.net/?f=E%5BX%5D%3D0%5C%2CP%28X%3D0%29%2B1%5C%2CP%28X%3D1%29%2B%5Ccdots%2B4%5C%2CP%28X%3D4%29)
![E[X]=1.4](https://tex.z-dn.net/?f=E%5BX%5D%3D1.4)