Pearson Algebra 1 Common Core, 2011
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Pearson Algebra 1 Common Core, 2011 View details
7. Exponential Growth and Decay
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Exercise 14 Page 464

Practice makes perfect
We can model the population of frogs by using the exponential growth function. P(t)= a(1+ r)^tThe function can be used to find the population of frogs P(t) after t years, where a is the initial number of frogs and r is the percent rate of change.We know the initial number of frogs and the percent rate of change, which are 100 and 22 %. Then, a= 100 and r= 0.22. P(t)= 100(1+ 0.22)^t ⇔ P(t)=100(1.22)^t Now that we have the function, we can find the number of frogs in 5 years by substituting 5 for t.
P(t)=100(1.22)^t
P( 5)=100(1.22)^5
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Simplify right-hand side
P(5)=100(2.70270 ...)
P(5)=270.27081 ...
P(5)=270
The number of frogs will be 270 in 5 years.
The function P(t)=100(1.22)^t represents the yearly increase where t is the number of years. To write an expression representing equivalent monthly increase rate, we will use the fact that there are 12* t months in t years. Let's start by rewriting the exponent as 12t12.
(1.22)^t
(1.22)^(12t12)
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Simplify
(1.22)^(112 * 12t)
(1.22^(112))^(12t)
(1.01670 ...)^(12t)
(1.017)^(12t)
Now let 12t= m. Then, we have (1.017)^(12t) ⇔ (1.017)^m We have found an expression of the form r^m, where r is approximately the monthly growth factor and m is the number of months.