At the beginning of the school year, there were three 4th grade classes. mrs. smith’s class had 19 children, mr. day’s class has 17 children, and ms. brown’s class had 20 children. at the end of the year there were still three classes, but 13 children had moved during the year. how many total students were left at the end of the year?

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