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.
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Produce tgere own food
<span>Extreme temperature and bedrocks
Tundra and desert both have shallow soil profiles because of the extreme temperatures and the bedrocks it has. In the case of tundra, it has extreme cold temperature and the soil were covered in ice in long periods of time. Because of this, the plants were unable to get water from the bedrocks resulting in plants dying. In the desert, however, it has extreme hot temperature making the plants unable to survuve due to lack of water in the environment and in the bedrocks. The plants that can only survive in this temperature are the plants that has the ability to store water in their system.</span>
The EPA is an independent agency formed for environmental protection. Hence the statement The Clean Air Act would be a reason for the Environmental Protection Agency (EPA) to regulate car emissions is true.
Car emissions are very harmful for all the living organisms in an environment.
The correct answer is: a tourniquet.
The tourniquets are tight straps around an arm or leg and tightened to stop bleeding, used to control arterial and venous blood flow. In the past, tourniquet are used to control bleeding during amputations. Now, a tourniquet is used in surgeries to block arterial blood flow following and to minimize blood loss.