Question

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A scientist is measuring the amount of radioactive material in an unknown substance. When he begins measuring, there are 12.8 grams of radioactive substance. 9 days later, there are 7.33 grams. After 14 days, there are 5.38 grams. After 30 days, there are 2.00 grams. Assuming that the decay is exponential, find the equation that determines the number of grams remaining after x days and use the equation to determine the amount of radioactive material remaining after 50 days.
A. 0.56 g
B. 0.58 g
C. 3.27 g
D. 3.33 g

Answer 1

@agent0smith could you help me?

Answer 2

You'll have to tell me a bit about the course it is from... are you fitting a line of best fit to the data? or just finding an equation using a couple of points?

Answer 3

fnding the equation using a couple of points I believe

Answer 4

Okay. Does this look familiar? \[\Large A = A_o e^{rt}\]if not post more info, these questions vary depending on your course

Answer 5

This is the Half life formula

Answer 6

yep it looks fmiliar

Answer 7

Initial amount is 12.8, so Ao is 12.8\[\Large A = 12.8 e^{rt}\]9 days later, there are 7.33 grams - when t= 9, A=7.33:
\[\Large 7.33 = 12.8 e^{9r}\]we need to find r

first divide both sides by 12.8

Answer 8

thanks so much!!!

Answer 9

I GOT IT FROM THEIR!!:)

Answer 10

You got r? by taking logs of both sides? good job!