Exponential Growth and Decay

Which of the following equations represents exponential growth? Choose all that apply.

Which of the following equations represents exponential decay? Choose all that apply.

The equation $$A=125\left(\frac{1}{2}\right)^{\frac{t}{50}}$$  gives the amount, in grams, of a radioactive substance remaining after t years. How many grams of the substance was there initially?

(a)  

The mice population is 25,000 and is decreasing by 20% each year. What will be the mice population after 3 years?

Your new computer cost $1500 but it depreciates in value by about 18% each year. How much will your computer be worth in 6 years? (Round to the nearest cent.)

Write an equation that models the following situation:

Samantha's hair was known to grow very rapidly. It began at a length of 6 inches and grew at a rate of 14% a week.