# A lab has 40 kg of radioactive uranium this substance has a half-life of 8 minutes and decays exponentially. How do you find the decay constant k?

##### 1 Answer

Jul 16, 2017

Starting with the equation:

Substitute the value of

Divide both aides of the equation by

You use the fact that

We can eliminate the exponential by using the natural logarithm on both sides:

We know that ln(1/2) = -ln(2) and the inverses will disappear on the right:

Flip the equation and divide by