Ok so
for a thing that is P amount at first, with a half life of k days
after t days, the amount left is A
the equation is
![A=P( \frac{1}{2})^{ \frac{t}{k} }](https://tex.z-dn.net/?f=A%3DP%28%20%5Cfrac%7B1%7D%7B2%7D%29%5E%7B%20%5Cfrac%7Bt%7D%7Bk%7D%20%7D%20)
given
13% of P remained=A
t=400
replace A with 0.13P and t with 400
0.13P=
![P( \frac{1}{2})^{ \frac{400}{k} }](https://tex.z-dn.net/?f=P%28%20%5Cfrac%7B1%7D%7B2%7D%29%5E%7B%20%5Cfrac%7B400%7D%7Bk%7D%20%7D%20)
divide both sides by P
![0.13=( \frac{1}{2})^{ \frac{400}{k} }](https://tex.z-dn.net/?f=0.13%3D%28%20%5Cfrac%7B1%7D%7B2%7D%29%5E%7B%20%5Cfrac%7B400%7D%7Bk%7D%20%7D%20)
take the ln of both sides
![ln0.13=( \frac{400}{k})ln \frac{1}{2}}](https://tex.z-dn.net/?f=ln0.13%3D%28%20%5Cfrac%7B400%7D%7Bk%7D%29ln%20%5Cfrac%7B1%7D%7B2%7D%7D%20)
multiply both sides by k
![kln0.13=400ln \frac{1}{2}}](https://tex.z-dn.net/?f=kln0.13%3D400ln%20%5Cfrac%7B1%7D%7B2%7D%7D%20)
divide oth sides by ln0.13
k=
![\frac{400ln \frac{1}{2} }{ln0.13}](https://tex.z-dn.net/?f=%20%5Cfrac%7B400ln%20%5Cfrac%7B1%7D%7B2%7D%20%7D%7Bln0.13%7D%20)
evaluate
k=135.897 days
the half life is 135.897 days
55:86
Step-by-step explanation:
86+55=123 so ratio is from girls to boys
Answer:
isn't
can't
Step-by-step explanation:
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There’s 100 students in the drama club and 84 students in the yearbook club