# Question #5d643

##### 2 Answers

Jan 18, 2017

4052 years old.

#### Explanation:

25% is half of half life. so 2 to the .5 of a half life.

So the amount of the carbon left. is

Feb 6, 2017

The sample is 2380 years old.

#### Explanation:

We can express the rate law for a first-order decay as

where

We can rewrite this as

If the concentration of carbon-14 has decreased by 25 %, then 75 % remains.

The sample has decayed for 0.4150 half-lives.