Question

does anyone know how to use excel for exponential decay and logs?

Answer 1

In order to understand the prehistory of the Hawaiian island of Lana'i better, anthropologists Maria Sweeney, Melinda Allen, and Boyd Dixon used radiocarbon dating on charcoal found in an ancient dwelling site, the Kaunolu Village National Historic Landmark, the largest archeological complex on the island. In one of their samples, they found that approximately 94% of the original carbon 14 remained. Using the fact that Carbon 14 decays by 1.202% every 100 years, determine the approximate age of the this sample . In your word document, paste the Excel table you made to come up with your answer.

Answer 2

exponential growth and decay

Answer 3

you can either use a predefined function, or define one yourself i believe

Answer 4

no clue what that means heres what i know so far 100(1-.01202)^1

Answer 5

what is the data that you need to make a table with?

Answer 6

well thats the data up there

Answer 7

thats not data to make a table with, thats information regarding carbon 14 and how much is left in the stuff

Answer 8

hey jake whats up

Answer 9

yea i need to create a table from that information

Answer 10

you need to make a table of values to do the Excel part... your formula is part of making that table :)
Hey how are you :) ?

Answer 11

not too good im stuck on this problem about exponential decay i just need a couple reminders to resurface my memory

Answer 12

@amistre64 you can take this from here if you want... I'm not super strong on the compounding/exponential decay stuff... but I'd like to see how to do it.

Answer 13

im sure i can come up with an age, but i got no idea about this table thing

Answer 14

well i can come up with the formula chart on excel by myself i think cuz i have the notes im just stuck on the problem itself for now

Answer 15

weight remaining is a function of age, which is really a statement of how many 100-year cycles have elapsed

Answer 16

so the table is weight remaining vs. age or something like that

Answer 17

was 100(1-.01202)6 correct or is it 94(1-.01202)

Answer 18

essentially evaluate the loss of material through decay at each 100 year step, creating ordered pairs

Answer 19

then "by inspection" determine how many 100 year cycles it takes to get down to 94% remaining

Answer 20

so was 100(1-.01202)6 correct or is it 94(1-.01202)?

Answer 21

after 2 cycles, the Excel formula would calculate the row 1 answer - 1.202% of the row 1 answer to get the row 2 amount remaining

Answer 22

(sorry, ugly drawing there...)

Answer 23

Jakes seems to have a grasp on it :)

Answer 24

Everything but how to actually solve vs. using inspection/Excel :)

Answer 25

hmmm so the 94% is a nonfactor?

Answer 26

Excel is good for building intuition... it's not a good analytical approach :)

Answer 27

Doesn't matter here though, since the problem specifically says to use Excel to estimate the age

Answer 28

i wonder if i have to use the relative change formula for this

Answer 29

wow............ i am so lost what is the answer maybe i can figure out how to work my way up from there

Answer 30

In the Excel cell in the column for "amount remaining", you need to calculate that by subtracting 1.202% of the previous amount FROM the previous amount.

you just have to put in the first amount as 100%, no calculating. (put this in cell B1)
Then the next amount formula in cell B2 should be =B1(1-1.0202%) or =B1(1-0.010202)

Answer 31

maybe something like this

Answer 32

It's like calculating that stock price drop from yesterday, except repeating over and over again until you get down to 94% of the original

Answer 33

Nice! @amistre64

Answer 34

i used the reiterations of

\[B_{n+1}=B_n-B_n(.01202)\]

Answer 35

@yomamabf does that spreadsheet help explain it?

Answer 36

yes i think it does im lookin over the formula he used

Answer 37

so the formula wouldnt be 100(1-.01202)?

Answer 38

or was that anothe way of writing it?

Answer 39

just another way of writing it.

Answer 40

yes, yours is factored, the other is "multiplied out"

Answer 41

u guys are awesome thanx let me let this sink in and plug it in to excel

Answer 42

good luck

Answer 43

sorry jake lol only room for 1 medal i gave u one yesterday *wink* =P

Answer 44

While it's sinking in, reflect on that stock price drop problem too :) That was a SINGLE drop (at least I hope!!!) and this is like that, but it is a series of drops of 1.202% off each previous amount

Answer 45

;)

Answer 46

thank u <3333

Answer 47

any time :)

Answer 48

hey jake wait so would this be 500 years old since we're going by 100 years

Answer 49

You are quite smart :) good catch!

Answer 50

each successive drop comes after 100 years, so you count the # of drops, but the REAL answer is how old, not how many drops, so it's 500 years, not 5 drops, and definitely NOT 5 years

Answer 51

yep kk

Answer 52

I think I dodged an arrow there... glad I didn't say "5 years" earlier ;)

Answer 53

lolol