Question

A tumor is injected with 0.1 grams of lodine-125, which has a decay rate of 1.15% per day. To the nearest day, how long will it take for half of the lodine-125 to decay?

days

Answer 1

hi,

1 - 0.015 = 0.985

so we have : 0.1 *0.985 ^n = 0.05

0.985^n = 0.05 /0.1

0.985^n = 0.5

n = ln (0.5) /ln (0.985)

n ≈ 46

Let's check : 0.1*0.985^46 ≈0.0498