graph shows it can you please help me

Question

The graph below shows the decay rate of a 100 gram sample of strontium-90. According to the graph, how many grams of strontium-90 remain after 2 half-lives?

Correct unit Incorrect

Answer 1

After 1 half-life, 50% should remain.

After a second half-life, 50% of that remains, (0.5)(0.5)= 0.25 = 25%.

the half-life shown here is 25 years.