The equation for radioactive decay is,

.

Where is the original amount of a radioactive substance, is the final amount, is the half life of the substance, and is time.

The half life of Carbon-14 is about years. If a fossile contains grams of Carbon-14 at time , how much Carbon-14 remains at time years?

The number of butterflies in an exhibit is decreasing at an exponential rate of decay. The number of butterflies is decreasing by every year. There are butterflies in the exhibit right now. How many butterflies will be in the exhibit in years?

The number of fish in an aquarium is decreasing with exponential decay. The population of fish is decreasing by each year. There are fish in the aquarium today. If the decay continues how many fish will be in the aquarium in years?

The population of a city is decreasing. The city has a population of , people today, but the population decreases by every year. What will be the population of the city in years if this continues?

There is water leaking out of a cup. of the water is leaking out every minute. How many kilograms of water will be left in minutes and seconds, if there are kilograms of water ,, in the cup right now?

An animal population is dying out. There is a decrease in this number of animals by every year. In years, there will be of this animal left. What is the current population of this animal today?

A school is losing a certain number of students each year. This year, the school has students. Four years ago the school had students. The yearly rate of the school losing students has been the same for the last four years. What is the school's yearly rate of losing students?

Over the past few years, the number of students enrolled at a certain university has been decreasing. Each year there is a 12% decrease in student enrollement. Currently, 14,286 students are enrolled. If this trend continues, how many students will be enrolled in 5 years?

Suppose 5 milligrams of element X decays to 3.2 milligrams after 48 hours. What is the decay rate on a day to day basis?

An element has a half life of 6 days. What is the approximate amount remaining for a 50 mg sample of this element after 5 days?