# Question #e627c

##### 1 Answer

Jul 6, 2017

37.44 days

#### Explanation:

We can use the direct formula for this, or use a simple arithmetic ratio if the amounts work out well. The definition of half-life is the time it takes for half of the substance to decay. Thus, after one (1) half-life,

Putting them together we conveniently get our desired

With a half-life of 18.72 days, this amount of decay will occur in 37.44 days.