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Example Questions
Example Question #1 : Other Exponent Applications
A biologist figures that the population  of cane toads in a certain lake he is studying can be modeled by the equation
,
where  is the number of days elapsed in 2015. For example,Â
 represents January 1, Â
 represents January 2, and so forth.
If this model continues, in what month will the population of cane toads in the lagoon reach 5,000?
May
June
April
March
FebruaryÂ
March
Set  and solve forÂ
 :
January and February have 59 days total; add March, and this is 90 days. The 76th day is in March.
Â
Example Question #21 : Applying Exponents
A biologist figures that the population  of cane toads in a certain lake he is studying can be modeled by the equation
,
where  is the number of days elapsed in 2015. For example,Â
 represents January 1, Â
 represents January 2, and so forth.
Assuming that this has been the model for their growth throughout the previous year as well, in what month did the population hit 100 cane toads?
October 2014
November 2014
December 2014
August 2014
September 2014
December 2014
Set  and solve forÂ
:
17 days before January 1 was in December of 2014.
Example Question #3 : Other Exponent Applications
Lucia deposits $40,000 into a savings account that pays 5.5% annual interest compounded continuously. Assuming she neither deposits nor withdraws money, how long will it take for her to have $60,000 in the account?
Between 6 and 7Â years
Between 9 and 10Â years
Between 7 and 8 years
Between 8 and 9Â years
Between 5 and 6 years
Between 7 and 8 years
We set final principal  original principalÂ
, and interest rateÂ
. We solve forÂ
 in the  continuous compound interest formula:
The correct response is therefore between 7 and 8Â years.
Example Question #2 : Other Exponent Applications
Ann deposits $30,000 into a savings account that pays 4.5% annual interest compounded quarterly. Assuming she neither deposits nor withdraws money, what is the amount of time it will take for her to have at least $50,000 in the account?
Apply the compound interest formula:
.
We set final principal  original principalÂ
, interest rateÂ
, number of periods per yearÂ
 (quarterly). We solve forÂ
 in the equation
This is rounded up to  the next quarter of a year, so the correct response is 11.5 years, or 11 years 6 months.
Example Question #1 : Other Exponent Applications
A company is constructing a wall with 4-sides, all sides are of equal length.Â
Write an equation using exponents to calculate the area of the wall. Use  as the length and height.
The formula to find area is:
 is correct.
In our case our length is equal to our width which is .
Substituting our values into our equation we get:
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