Final answer:
To calculate the population of rabbits from 2 years ago with an annual decrease of 20%, work backwards to increase the current population of 70 rabbits by 25% each step. The population from 1 year ago would be 87 rabbits, and from 2 years ago approximately 108 rabbits, with the closest provided option being 110 rabbits.
Step-by-step explanation:
A student has asked how many rabbits were in a population 2 years ago if the population decreases by 20% each year, and this year there are 70 rabbits.
To find out the rabbit population from 2 years ago, we need to work backwards and calculate the population increase by 25% (since 80% is 20% less, so to get back to 100% we add 25%).
- Calculate the population from 1 year ago: Divide the current population by 0.8 (which is 100% - 20%). So, 70 / 0.8 = 87.5 rabbits. Since we can't have half a rabbit, we'll consider it 87 rabbits.
- Calculate the population from 2 years ago: Again, divide by 0.8. So, 87 / 0.8 = 108.75 rabbits. Rounding it down, we get 108 rabbits.
However, since none of the answer choices match the number 108 exactly, it indicates a potential error in the question or in the options provided. We would normally expect an exact integer answer for such a problem. Nevertheless, if we had to choose the closest answer from the options given, we would choose Option C: 110 rabbits, even though it is not the exact calculated value we obtained.