Exercise 65 Page 798

Practice makes perfect

a We are given that there are 425 members of a community swimming pool.

The number of visits to the pool is normally distributed with a mean of 90 and a standard deviation of 15. We will find the percent of the members went to the pool at least 45 times. We will use the Empirical Rule to help us visualize the data.

Finally, we will find the percent of the members by adding the percents of the shaded areas.

2.35 %+13.5 %+34 %+34 %+13.5 %+2.35 %+0.15 %

Add terms

99.85 %

The percentage of members that visited the pool at least 45 times is 99.85 %.

b We will find the probability of a member selected at random went to the pool more than 120 times.

We will evaluate the desired probability by adding the probabilities of the shaded areas.

p=2.35 %+13.5 %+34 %+34 %+13.5 %+2.35 %+0.15 %

Add terms

p=99.85 %

The probability of the randomly selected members who went to the pool more than 120 times is 2.5 %.

c Now we will find the percent of the members went to the pool between 75 and 105 times.

To find the percent of the members we will add the percents of the shaded areas.

p=34 %+34 %

Add terms

p=68 %

The percent of the members who visited the pool between 75 and 105 times is 68 %.

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