According to eMarketer, adults in the United States

spent an average of 92 minutes per day on social

media platforms Facebook, Snapchat, and Instagram

in 2017. Assume that minutes per day on these plat-

forms follow a normal distribution with a standard

deviation of 27 minutes.

a What is the probability that the amount of time spent

today on mobile devices by a particular U.S. adult is

1. less than 70 minutes?

2. more than 65 minutes?

3. between 85 and 110 minutes?

b. Confirm the answers to part a using Excel.

c. Which number of minutes per day represents the

75th percentile?