In an all boys school, the heights of the student body are normally distributed with a mean of 71 inches and a standard deviation of 4.5 inches. Using the empirical rule, what percentage of the boys are between 62 and 80 inches tall?

The weight of a radioactive isotope was 96 grams at the start of an experiment. after one hour, the weight of the isotope was half of its initial weight. after two hours, the weight of the isotope was half of its weight the previous hour. if this pattern continues, which of the following graphs represents the weight of the radioactive isotope over time? a. graph w b. graph x c. graph y d. graph z