The half-life of halfnium-156 is 0.025 seconds. What was the original amount of the substance if after 0.1 seconds 3.125 gram remains? (A: 25 g)

9.9 years

a = p(1 + rt) . . account balance after time t at rate r starting with principal p

3000 = 2500(1 + 0.0202t) . . filling in the given numbers

1.2 = 1 + 0.0202t . . divide by 2500

0.2 = 0.0202t . . . subtract 1

0.2/0.0202 = t ≈ 9.901

it will take about 9.9 years for the account balance to reach $3000.

this is more of a statement than a question. is there answers to go along with this, or is it opinion based?