Answer:

Explanation:
We are asked to find how much of a 40 gram sample remains after 12 years.
Iron-55 has a half-life of 3 years. Therefore, after 12 years, 4 half-lives have been completed.
- 12 years/3 years = 4 half-lives
Every time a half-life is completed, half of the sample's mass decays. Remember we start with a 40 gram sample.
- 1 half- life: 40 g / 2 = 20 g
- 2 half-lives: 20 g / 2= 10 g
- 3 half-lives: 10 g / 2 = 5 g
- 4 half-lives: 5 g / 2 = 2.5 g
There is also a formula that can be used to solve this problem.

Where A₀ is the initial amount, t is the time, and hl is the half-life.
We know 40 grams is the inital amount, 12 years is the time, and 3 years is the halflife.




After 12 years, <u>2.5 grams </u> of Iron-55 will remain.
Answer:
A:true animals only perform cellular respiration and plants only perform cellular respiration
Answer:
a. veins and arteries
b.diaphragm
c.kidney
d.lung
e.4
f.left auricle(atrium) , right auricle(atrium)
g.left ventricle, right ventricle
h.blood plasma
i.digestive
j.buccal cavity ,saliva
k.bile
l.excretory
m.kidneys
Explanation:
Polio affects the central nervous system and spinal cord. It can cause muscle weakness and paralysis. Polio is a life threatening condition because it can paralyze the muscles that help you breathe.
The polio vaccine is used to help prevent these diseases in children and adults.
Carbon debt, caused by CO2<span> i know that is one of them </span>