A line graph is drawn where x-axis is 'Time (billions of years)' ranges from 0 to 5 in increment of 1 and y-axis is 'Fraction of Potassium-40 Present' ranges from 0 to 1 in increment of one fourth. The curve starts from (0 comma 1) passes through (1.2 comma one half) marked as Half-life 1, (2.5 comma one fourth) marked as Half-life 2, (3.7 comma one eighth) marked as Half-life 3, and ends at (5 comma one sixteenth).