The mean of a probability distribution is 50 and the standard deviation is 5. What percent of the observations lie between 45 an 55? What percent of

The mean of a probability distribution is 50 and the standard deviation is 5.

1. What percent of the observations lie between 45 an 55?
2. What percent of the observations lie between 40 and 60?
3. What percent of the observations lie between 35 and 65?