Cumulative Exam — Cumulative exam Answers

Two different radioactive isotopes decay to 10% of their respective original amounts. Isotope A does this in 33 days, while isotope B does this in 43 days. What is the approximate difference in the half-lives of the isotopes?

Out of a population of 1,000 students, 80 were asked by a random sampling what color they would prefer for their first car. Their responses are shown in the table below.Car ColorFavorite ColorNumber of StudentsBlue5Red18Gray27Silver14White16Using proportional reasoning, how many students out of the 1,000 would you expect to prefer a silver car?

One brand of vinegar has a pH of 4.5. Another brand has a pH of 5.0. The equation for the pH of a substance is pH = –log[H+], where H+ is the concentration of hydrogen ions. What is the approximate difference in the concentration of hydrogen ions between the two brands of vinegar?

A city’s annual rainfall totals are normally distributed, and the probability that the city gets more than 43.2 inches of rain in a year is given by . If the standard deviation of the city’s yearly rainfall totals is 1.8 inches, what is the city’s mean annual rainfall?

You just obtained a credit card. You immediately purchase a stereo system for $200. Your credit limit is $1000. Let’s assume that you make no payments and purchase nothing more and there are no other fees. The monthly interest rate is 1.42%.What is the growth rate of your credit card balance?a.0.42c.14.2b.0.0142d.142