# Radioactive decay of #""^40K# atoms in an igneous rock has resulted in a ratio of 25 percent #""^40K# atoms to 75 percent #""^40Ar# and #""^40Ca# atoms. How many years old is this rock?

##### 1 Answer

May 31, 2017

#### Answer:

2.5 x

#### Explanation:

Given K-40 remaining = 25% of original K-40 @ 100%

From

Solving for time of decay (t)