The initial amount of a substance is 267 grams. The amount of substance decreases by 12% every 8 years.
How many grams are left after 5 years?
What is the yearly decay factor?

What is the yearly decay rate?

Question

The initial amount of a substance is 267 grams. The amount of substance decreases by 12% every 8 years. 
How many grams are left after 5 years?
What is the yearly decay factor?

What is the yearly decay rate?

hero · Answer

You need the formula for decay factor and decay rate

anonymous · Answer

$$267\times (.82)^{\frac{5}{8}}$$ should do it for the first one

anonymous · Answer

unless you are supposed to write this as 
$$Q_0e^{kt}$$