A 18 gram sample of a substance that's used to detect explosives has a k-value of 0.1226

Given:

Initial mass = 18 g

k-value = 0.1226

The mass at time t (days) is

At half life, m = 18/2 = 9 g.

The time for half life is given by

Therefore

ln(1/2) = -0.1226t

Hence obtain

t = ln(1/2) / -0.1226

 = 5.654 days

5.7 days (nearest tenth)

or

For this problem, we use the formula for radioactive decay which is expressed as follows:

An = Aoe^-kt

where An is the amount left after time t, Ao is the initial amount and k is a constant.

We calculate as follows:

A0 = 18

An = 18/2 = 9

k = 0.125

9 = 18 e^-0.125t

0.5 = e^-0.125t

t = 5.55 days

answer: no, but if it does it's a obvious pattern.

step-by-step explanation: