Answer:
Step-by-step explanation:
As an example, iodine-131 is a radioisotope with a half-life of 8 days. It decays by beta particle emission into xenon-131. After eight days have passed, half of the atoms of any sample of iodine-131 will have decayed, and the sample will now be 50% iodine-131 and 50% xenon-131.
50 grams to 25 grams is one half-life. 25 grams to 12.5 grams is another half-life. So, for 50 grams to decay to 12.5 grams, two half-lives, which would take 36 days total, would need to pass. This means each half-life for element X is 18 days.
It's a geometric sequence.

It's the sum for term 4 through term 15.
Answer:
60,
Step-by-step explanation:
4.8 / 0.08
Removing the decimal points by multiplying by 100:
= 480 / 8
= 60.
2 and 4.5 is not equivilant since 2 and 4.5 cannot go together (the 0.5 does not help and so it does not make it equivalent.)
Hope this helped!
Nate