Marco's equation should be $10(2^{d})$ since the bacteria double each day. 10 is the starting value of the population. 2 is the growth rate of "double each day" with d as an exponent. This will double each day because:

Day 1 is $2^{1}=2$

Day 2 is $2^{2}=4$

Day 3 is $2^{3}=8$

Day 4 is $2^{4}=16$

You'll notice the value doubles each day.

Isabella has a different equation because her population increases by a percentage. We use the simple interest formula to calculate the bacteria's daily increase or interest.

1(1+0.2)d

1 is the starting population.

1+0.2=1.2 is the rate at which it grows each day.

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4 years ago

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Macy has a 20 year adjustable rate mortgage with a fixed rate for the first 7 years. In the 8th year, the interest rate rises to

Crank

The answer is indeed 3,725.90. The reason why is because with each adjustment, you take the remaining balance and calculate a fixed rate loan for the remaining time period at the new rate. When you follow that procedure with the data you already have, you get that answer.

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3 years ago

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