The half-life of Cu-61 is approximately 3 hours, meaning that after each half-life, half of the remaining sample decays. After 9 hours, which is three half-lives (3 hours x 3 = 9 hours), the original 2 mg sample would have gone through three decay cycles. Thus, the amount remaining would be (2 , \text{mg} \times \left(\frac{1}{2}\right)^3 = 2 , \text{mg} \times \frac{1}{8} = 0.25 , \text{mg}).
Three eighths is the same as six sixteenths - half of six sixteenths is three sixteenths
1/8th of a mg. You lose half every three hours.
triple
Three times.
three
times 3. For example, Three times as much of 7 is 3*7 = 21 Three times as much of 10 is 3*10 = 30
Three eighths is the same as six sixteenths - half of six sixteenths is three sixteenths
After three half-lives, 12.5% of the original radioactive material will remain. Each half-life reduces the amount of material by half, so after three half-lives the remaining material will be 0.5^3 = 0.125 or 12.5%.
The double is negated by the half, so you are still left with the original three-fourths.
Triple means three times as much.
A half-life is the amount of time it takes for half of the material to decay. So if you started with 80g After 1 half-life you would have 40 g After 2 half-lives you would have 20 g After three half-lives you would have 10 g
1/8th of a mg. You lose half every three hours.
triple
It's not half as much, it is twice as much. And it is twice as much, precisely because 2/3 is twice as much as 1/3.
Three times.
Three times.