Isabella puts 100 marbles in a jar and shook the jar. There are 4 colors of marbles. There are 25 of each color. What is the probability that Isabella will pick a marble out of the jar that is her favorite color?

The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a mean of $235 and a standard deviation of $20. according to the standard deviation rule, how much did almost all (99.7%) of the students spend on textbooks in a semester?