After two half-lives or 60 years, 7.5 g of the element will be left.
<u>Explanation:</u>
<u>Half-life:</u>
- In simple words, Half-life can be defined as the amount of time needed for a quantity to fall to half its value as contained at the beginning of the time period.
- In this problem the half-life of the element is thirty years, then after thirty years half of the sample would have decayed and half would be left as it is.
- After thirty years (The first half-life ) 30 /2 = 15 g declines and 15 g remains disappeared.
- And after another sixty years (The two half-lives) 15 /2 = 7.5 g declines and 7.5 g remains disappeared.
- After two half-lives or 60 years, 7.5 g of the element will be left.
Answer:
5%
Explanation:
The adrenal cortex in both males and females produce a small amount of weak androgens. One of the major weak androgen secreted by adrenal cortex is dehydroepiandrosterone (DHEA).
Levels of dehydroepiandrosterone secretion exhibit changes with age. The dehydroepiandrosterone secretion increases till the age of 20-24 years and falls off with increasing age after the age of 30 years in both males and females. The DHEA production at the age of 80 years is about 5% of its secretion at the age of 30 years.
The following which poses as the most logical conclusion about the life cycle of this plant is definitely : The plant is a fern, and the gametophyte is its dominant phase. I am pretty sure you will fing this answer interesting. Regards!
B THEY RELEASED CARBON DIOXIDE, WHICH EVOLVING ANIMALS NEEDED.
