Question

An isotope sample initially weighing 500 grams decays to produce a daughter element. What is the amount of parent element remaining after two half-lives?

Answer 1

The answer is 125 grams.

Step-by-step explanation:

Elements and substances decay in time and the amount of time for it to be half of it's initial amount is defined as "half-life of that substance".

In the example, the initial weight is 500 grams and we are asked to determine the amount after two half-lives, which after the first half-life is 500/2 = 250 grams and after the second one, 250/2 = 125 grams remains from the parent element.

I hope this answer helps.