Question #7c67b
1 Answer
The graph is not clear.
From the given graph Halflife is
Explanation:
Halflife
The accompanying graph shows the rate of decrease of the count rate or % samples remaining with time.
For any particular radioisotope the % samples remaining and time will be different. However, the shape of the curve will be the same.
In order to measure the halflife from a graph

Read the % samples remaining for zero days.
In our graph it is 100. 
Go down to half point where % sample remaining is 50 and draw a horizontal line meeting the curve.
Now draw a vertical line down from this point at the curve and read off the halflife where the vertical line meets the time axis.
From the given graph Halflife appears