Question

The half-life of a certain radioactive material is 38 days. An initial amount of the material has a mass of 497 kg.
Write an exponential function that models the decay of this material. Find how much radioactive material
remains after 4 days. Round your answer to the nearest thousandth.
(1 point)
A
; 462.029 kg
B
; 0.087 kg
C
; 1.040 kg
D
; 0 kg

Answer 1

You'll find this page helpful:
http://www.1728.org/halflife.htm

Ending Amount = Beginning Amount / 2^n
where n = number of half lives
4 days equals how many half lives (of 38 days)?

4/38 = 0.1052631579 half lives

Ending Amount = 497 kg / 2 ^ 0.1052631579
Ending Amount = 497 kg / 1.0756905862
Ending Amount = 462.0287714392 kg

Ending Amount = 462.029 (rounded)
answer is A