SOLUTION: Andrew measures the amount of a very unstable substance to be 100 moles. The half life of this substance is three days (after three days, half is gone). #1 Write an exponential

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Question 847275: Andrew measures the amount of a very unstable substance to be 100 moles. The half life of this substance is three days (after three days, half is gone).
#1 Write an exponential function that models this situation where y is the amount of substance and x is time in days.
#2 Use your equation to complete the chart.
Days
-3(3 days prior)
0
3
6
12
Amount (I need to determine the amounts)

#3 Use your data from the chart to graph your equation.
#4 Calculate the expected amount of substance if Andrew had taken his measurement 9 days earlier. Show your calculations and consider the trend of your graph.

Found 2 solutions by stanbon, Fombitz:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Andrew measures the amount of a very unstable substance to be 100 moles. The half life of this substance is three days (after three days, half is gone).
--------------------------------------
#1 Write an exponential function that models this situation where y is the amount of substance and x is time in days.
y = 100*(1/2)^x
------------------------------------------
#2 Use your equation to complete the chart.
Days
-3(3 days prior):: y = 100(1/2)^(-3) = 100(1/8) = 12.5
I'll leave the others to you.
0
3
6
12
Amount (I need to determine the amounts)
#3 Use your data from the chart to graph your equation.
graph%28400%2C400%2C-10%2C10%2C-10%2C10%2C100%281%2F2%29%5Ex%29
-------------------------------------------------------------
#4 Calculate the expected amount of substance if Andrew had taken his measurement 9 days earlier. Show your calculations and consider the trend of your graph.
y(-9) = 100(1/2)^-9 = 0.1953 moles
===============
Cheers,
Stan H.

Answer by Fombitz(32388) About Me  (Show Source):