The half-life of a radioactive isotope is 10 days. If 3.2 kg are present now, how much was present 30 days previous?
30 days is 3 half-lives. So, there is 1/2^3 = 1/8 as much now as 30 days ago.
That means you had 3.2*8 = ___ kg then.
A(1/2)^(30/10) = 3.2
I don't really get it but the only thing that I think might help is:
10/3.2=a
a*30= answer
oh- thx
That is not one of the answer choices. The choices are 12.8, 25.6, 6.4, 51.2
To calculate how much of the radioactive isotope was present 30 days ago, we need to understand the concept of a half-life.
The half-life of a radioactive substance is the time it takes for half of the initial amount of the substance to decay. In this case, the half-life of the radioactive isotope is 10 days.
To calculate the amount present 30 days ago, we can use the formula:
Amount before = Amount after × 2^(number of half-lives)
Since we want to know the amount 30 days ago, which is two half-lives earlier, we substitute in the given values:
Amount before = 3.2 kg × 2^(30/10)
Simplifying the exponent:
Amount before = 3.2 kg × 2^3
Calculating the exponent:
Amount before = 3.2 kg × 8
Therefore, 30 days ago, 25.6 kg of the radioactive isotope was present.