Question

a population of 430 animals decreases at an annual rate of 21%. find the multiplier for the rate of exponential decay.

Answer 1

If the original population does not change, yo can say the population stays at 100%, right? So if the 100% original population decreases by 21%, then yo have subtraction: 100% - 21% = 79%. That would be the decrease in population for the first year ONLY. To get a multiplier, change percent back to decimal: 79% x 100 = 0.79. That's your multiplier. So if you measured the decline over 4 years, you would write 430 x .79 x .79 x .79 x .79 = 167. Remember, round up after each multiplying, because you are talking about living animals. There's no such thing as half a mouse. If your teacher marks it wrong, and him or her to prove that half an animal can survive for a year until the next counting.