Complete the table shown to the right for the half life of a certain radioactive substance. Decay rate:1.5% per year=-0.015

The half life is ___ years

Given:

Decay rate: 1.5% per year = -0.015

To find:

The half life.

Solution:

The continuous exponential decay function is

where, a is initial value, -k is decay rate and t is time period.

For half life, ,

Dividing both sides by A.

Taking natural log on both sides.

Divide both sides by -0.015.

Therefore, the half life is 46 years.

its a straight line parallel to the time axis