1. When a ball is dropped on the floor the height of the ball will decrease after each bounce.  If the equation for a ball’s height is h − 8(0.875)b where b is the number of bounces, and h is the height of the ball in feet. What is the height of the 5th bounce?

A. 4.1 feet Correct! h = 8(.875)5 = 4.10
B. 4.7 feet Incorrect. This is the 4th bounce, h = 8(.875)4 = 4.7
C. 5.4 feet Incorrect. This is the 3rd bounce, h = 8(.875)3 = 5.4.
D. 35 feet Incorrect. Substitute 5 in for b and solve.


2. A biologist noticed that the population of bacteria in a sample doubled every day. If the initial population sample was 25 bacteria, which equation below represents the number of bacteria b after d days?

A. b = 25(2)d Correct! The biologist starts with 25 bacteria and doubles, a = 25 and b = 2.
B. b = 2(25)d Incorrect. The biologist starts with 25 bacteria and doubles, a = 25 and b = 2.
C. b = (2)d Incorrect. The biologist starts with 25 bacteria and doubles, a = 25 and b = 2.
D. b = (25)d Incorrect. The biologist starts with 25 bacteria and doubles, a = 25 and b = 2.


3. Mrs. Bigby invested money that doubled in value every 12 years. If she invested $5,000 on the day of her son's birth, which equation below represents the amount of money, a, in the account after t years?
A. a = 5000(12)t Incorrect. The 5000 is the correct balance but the money doubles every 12 years.
B. a = 12(5000)t Incorrect. The 5000 is the balance and the money doubles.
C. a = 5000(2)t Incorrect. The 5000 is the correct balance but the money doubles every 12 years.
D. a = 5000(25)^ t 12 Correct! The 5000 is the initial amount; the money doubled every 12 years.


4. The metastable form of Technetium-99 (Tc-99m) is used in nuclear medicine procedures. It decays, losing half its mass every hour. If a doctor checks in on a patient six hours after the isotope is administered and 0.10 microgram of it still remains, which is closest to the amount of Tc-99m administered to the patient?

A. 6.4 micrograms Correct! The medicine losses half its mass after 6 hours, there is 0.10 micrograms left, the equation is 0.10 = b(.5)6. Divide 0.10 by (0.5)6.
B. 3.2 micrograms Incorrect. The medicine losses half its mass until there is 0.10 micrograms left, the equation is 0.10 = b(.5)6. Divide 0.10 by (0.5)6.
C. 0.333 micrograms Incorrect. The medicine losses half its mass until there is 0.10 micrograms left, the equation is 0.10 = b(.5)6. Divide 0.10 by (0.5)6.
D. 0.008 micrograms Incorrect. The medicine losses half its mass until there is 0.10 micrograms left, the equation is 0.10 = b(.5)6. Divide 0.10 by (0.5)6.