Here we can say that radioactive half lives, which is T1/2. It's just the amount of time required for half of a radioisotope to decay. Now a radioisotope or nuclide is just an isotope that has an unstable nucleus and emits radiation as it decays. Alpha decay, beta decay, electron capture, positron emission etcetera.
Based on this, if we take a look here, the example says what is the half life of the radioisotope that shows the following data of remaining percentages versus time. So here we have our percentage remaining and here we have number of days. We start out with 100% of our starting material on day zero. Remember, Half Life looks at how much time it takes us to lose half, all right, So 100, half of that would be 50. Half of that would be 25%. Another half of that would be 12.5%.
What are the number of days that separate each one of these percentages? Well, day zero. It takes three days for us to lose half. Looks like it takes another three days to lose half, and it looks like it took another three days to lose half. So based on this chart here, it looks like the half life is equal to 3 days for this particular radioisotope.