Calcium-49, a radioactive isotope, has a half-life of 9 minutes. If an 80-gram sample of the isotope decays for 27 minutes, how many grams of the original sample remain? Select one:
a. 60
b. 10
c. 40
d. 20

24. a sports ball is inflated to an internal pressure of 1.85 atm at room temperature (25 °c). if the ball is then played with outside where the temperature is 7.5 °c, what will be the new pressure of the ball? assume the ball does not change in volume nor does any air leak from the ball a) 0.555 atm b) 1.74 atm c) 1.85 atm d) 1.97 atm