Question

Medal!!!!

A scientist is measuring the amount of radioactive material in an unknown substance. When he begins measuring, there are 56.8 grams of radioactive substance. 12 days later, there are 55.45 grams. After 25 days, there are 54.03 grams. After 41 days, there are 52.32 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 500 days.
A. 2.21 g
B. 2.25 g
C. 12.65 g
D. 20.90 g
is B the correct answer?

Answer 1

A(x)=c edx

x stands for the number of days that have gone by, and
c and d are constants you pick so the equation will match the data

to find them, list a table of "days" and "amount" given in the problem

day amount (grams)
0 12.8
9 7.33
14 5.38
30 2.00


now use the first set of numbers: set x=0 and the amount to 12.8
A(x)=c edx12.8=c ed⋅012.8=c e0


can you solve for c ?

Answer 2

how would i go about solving for C?

Answer 3

set x= 0
amount to 12.8 A(x)=c
edx12.8=c
ed * 012.8= ce0
Does that clarify a bit more better ?

Answer 4

yea, i just dont get the order it needs to be put in to solve it

Answer 5

I don't really know any more ways to show it to you
sorry :(

Answer 6

ok well i know we can rule out C

Answer 7

we can rule out B to

Answer 8

okay so from my calculator im getting 20.90

Answer 9

?

Answer 10

@trantom

Answer 11

@jim_thompson5910

Answer 12

is D right or not?