Interest Equations - Algebra II
Card 0 of 13
Peter opens a savings account on his 
t birthday. He makes a deposit of 
. The account earns 
percent interest, compounded annually. Peter plans to take the money out when he is 
years old. If he doesn't make any deposits or withdrawals until then, how much money will be in the account?
Peter opens a savings account on his 
The formula for calculating compount interest is as follows:
where
= future value
= present value
= interest rate
= number of times the interest is compounded
In this problem, the present value of the money is $5000, and the interest rate is 7%. If Peter takes the money out when he is 50, it would have been compounded 29 times (once per year). Therefore:
The formula for calculating compount interest is as follows:
where
In this problem, the present value of the money is $5000, and the interest rate is 7%. If Peter takes the money out when he is 50, it would have been compounded 29 times (once per year). Therefore:
Compare your answer with the correct one above
Catherine invests $3500 in an investment account. The account earns 10% interest, compounded quarterly. After 5 years, how much money will she have?
Catherine invests $3500 in an investment account. The account earns 10% interest, compounded quarterly. After 5 years, how much money will she have?
The formula for calculating the future value of an interest earning account is
,
where
= future value,
= present value,
= annual interest rate,
= number of times the interest is compounded per year, and
= the number of years that have passed.
The problem asks for the amount of money in the account after 5 years, with 10% interested compounded four times per year (quarterly).
Plug in the given quantities and simplify:
The formula for calculating the future value of an interest earning account is
where
The problem asks for the amount of money in the account after 5 years, with 10% interested compounded four times per year (quarterly).
Plug in the given quantities and simplify:
Compare your answer with the correct one above
Felicia put money in a saving account with a 5% interest rate, compounded annually. After five years, she had $10,000. How much was her initial investment?
Felicia put money in a saving account with a 5% interest rate, compounded annually. After five years, she had $10,000. How much was her initial investment?
The formula for finding the future value of an investment is
,
where
= future value,
= present value,
= interest rate, and
= number of times interest is compounded.
Plug in the given numbers and solve for the present value:
The formula for finding the future value of an investment is
where
Plug in the given numbers and solve for the present value:
Compare your answer with the correct one above
Round the answer to two decimals.
Anthony put 
,
in his savings account today. The bank pays interest of 
every year.
How much does he have in his savings account after 
years?
Round the answer to two decimals.
Anthony put
How much does he have in his savings account after
The formula for computing interest is:
Beginning Amount x ((1 + rate)^number of years) = Ending Amount After number of years
Make sure to convert the rate from percent to number: 3% = 0.03
So the answer is 
The formula for computing interest is:
Beginning Amount x ((1 + rate)^number of years) = Ending Amount After number of years
Make sure to convert the rate from percent to number: 3% = 0.03
So the answer is
Compare your answer with the correct one above
Jamie deposits $5000 into an account at ABC bank. The account will earn a 4% interest rate compounded yearly. Jamie would like to withdraw the accumulated amount after 5 years and close the account. How much money would Jamie withdraw after 5 years? (Round your answer to the nearest dollar)
Jamie deposits $5000 into an account at ABC bank. The account will earn a 4% interest rate compounded yearly. Jamie would like to withdraw the accumulated amount after 5 years and close the account. How much money would Jamie withdraw after 5 years? (Round your answer to the nearest dollar)
Initial amount = 5000
The account earns 4% compounded yearly ===> Each $1.00 will grow into $1.04.
Growth rate = 1.04
Jamie will withdraw the money after 5 years. Since the interest is compounded yearly, the number of periods is equal to the number of years the money will be in the account.
number of periods = 5
From the above information, we can calculate the amount accumulated (or final amount) after 5 years using the following formula:
final amount = initial amount * (growth rate)number of periods
Initial amount = 5000
The account earns 4% compounded yearly ===> Each $1.00 will grow into $1.04.
Growth rate = 1.04
Jamie will withdraw the money after 5 years. Since the interest is compounded yearly, the number of periods is equal to the number of years the money will be in the account.
number of periods = 5
From the above information, we can calculate the amount accumulated (or final amount) after 5 years using the following formula:
final amount = initial amount * (growth rate)number of periods
Compare your answer with the correct one above
For coninuous compound interest:
Where
If an initial deposit of 
is continuously compounded at a rate of 
for 
years, what will be the final principal value to the nearest dollar?
For coninuous compound interest:
Where
If an initial deposit of
Using the equation for continuous compound interest and the given information, we get
Using the equation for continuous compound interest and the given information, we get
Compare your answer with the correct one above
Remember 
If an account has a starting principle P = $5,000, an interest rate r = 12% or 0.12, compounded annually, how much money should there be after five years? Assume no money has been added or taken out of the account since it was opened.
Remember
If an account has a starting principle P = $5,000, an interest rate r = 12% or 0.12, compounded annually, how much money should there be after five years? Assume no money has been added or taken out of the account since it was opened.
is the compound interest formula where
P = Initial deposit = 5000
r = Interest rate = 0.12
n = Number of times interest is compounded per year = 1
t = Number of years that have passed = 5
Round to the nearest cent or hundredth is 
.
P = Initial deposit = 5000
r = Interest rate = 0.12
n = Number of times interest is compounded per year = 1
t = Number of years that have passed = 5
Round to the nearest cent or hundredth is
Compare your answer with the correct one above
Julio invests $5000 into an account with a 2.5% interest rate, compounded quarterly. What is his account balance after 1 year (rounded to the nearest cent)?
Julio invests $5000 into an account with a 2.5% interest rate, compounded quarterly. What is his account balance after 1 year (rounded to the nearest cent)?
To determine Julio's account balance, we must use the interest formula given below:
where P is his principal (initial) investment, r is the interest rate (as a decimal), n is the number of times the interest is compounded, and t is the amount of time elapsed.
Plugging in all of our given information into the above formula - knowing that quarterly means four times a year - we get
To determine Julio's account balance, we must use the interest formula given below:
where P is his principal (initial) investment, r is the interest rate (as a decimal), n is the number of times the interest is compounded, and t is the amount of time elapsed.
Plugging in all of our given information into the above formula - knowing that quarterly means four times a year - we get
Compare your answer with the correct one above
Martisha invests $2000 into an account with continuously compounded interest. The account has an interest rate of 2.5%. Find the balance of the account after 2 years, rounded to the nearest cent.
Martisha invests $2000 into an account with continuously compounded interest. The account has an interest rate of 2.5%. Find the balance of the account after 2 years, rounded to the nearest cent.
To find the balance, B, of a continuously compounded interest account after a certain amount of time, we must use the following formula:
, where P is the initial investment, r is the interest rate (as a decimal), and t is the amount of time being considered.
Plugging in all of the given information, we get
which rounded becomes $2102.54
To find the balance, B, of a continuously compounded interest account after a certain amount of time, we must use the following formula:
Plugging in all of the given information, we get
which rounded becomes $2102.54
Compare your answer with the correct one above
How long will it take for Nikki to triple her initial investment into a continuously compounded interest account with an interest rate of 1.9%?
How long will it take for Nikki to triple her initial investment into a continuously compounded interest account with an interest rate of 1.9%?
The formula to find the balance, B, of a continuously compounded interest account with interest rate, r, after a certain time, t, is given by
To solve this problem, we need to know only the initial investment (P), our final balance (three times P) and the interest rate (expressed as a decimal), 0.019.
Plugging in our known information into the formula for continuously compounded interest, we get
We now solve for t:
Exponentiating both sides allows us to get rid of the exponential:
The formula to find the balance, B, of a continuously compounded interest account with interest rate, r, after a certain time, t, is given by
To solve this problem, we need to know only the initial investment (P), our final balance (three times P) and the interest rate (expressed as a decimal), 0.019.
Plugging in our known information into the formula for continuously compounded interest, we get
We now solve for t:
Exponentiating both sides allows us to get rid of the exponential:
Compare your answer with the correct one above
Sheila wants to double her initial investment into a compounded interest account, with an interest rate of 4%. How long will this take, if the interest is compounded annually?
Sheila wants to double her initial investment into a compounded interest account, with an interest rate of 4%. How long will this take, if the interest is compounded annually?
To determine the amount of time needed to double the initial investment - P - into a compound interest account, we simply plug in our given information into the formula:
where B is the balance, P is the initial investment, r is the interest rate (as a decimal), n is the number of times the interest is compounded, and t is the time elapsed.
Now, because we are doubling P, our balance B becomes two times P:
Now, we can solve for P:
To bring the time variable down from being an exponent, we take the logarithm of both sides (common or natural):
To determine the amount of time needed to double the initial investment - P - into a compound interest account, we simply plug in our given information into the formula:
where B is the balance, P is the initial investment, r is the interest rate (as a decimal), n is the number of times the interest is compounded, and t is the time elapsed.
Now, because we are doubling P, our balance B becomes two times P:
Now, we can solve for P:
To bring the time variable down from being an exponent, we take the logarithm of both sides (common or natural):
Compare your answer with the correct one above
If a person deposits 300 dollars to a savings account, which earns one percent interest that is compounded annually, what is the balance after 60 years?
If a person deposits 300 dollars to a savings account, which earns one percent interest that is compounded annually, what is the balance after 60 years?
Write the formula for compound interest.
Substitute all the known values into the formula.
The answer is: 
Write the formula for compound interest.
Substitute all the known values into the formula.
The answer is:
Compare your answer with the correct one above
Suppose Billy's has 
, invests the money at a bank at 
, compounded monthly. About how much will Billy have after 36 months?
Suppose Billy's has
Write the compound interest formula.
where 
is the total, 
is the principal, 
is the rate, 
is the number of times compounded annually, and 
is the time in years.
Substitute all into the equation.
The answer is: 
Write the compound interest formula.
where
Substitute all into the equation.
The answer is:
Compare your answer with the correct one above