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Sarah takes out a $38,876 loan for college. It has a 6.6% interest rate and compounds annually. The loan interest doesn’t start until after she graduates.

When she graduates, Sarah only makes enough money to pay for her basic necessities (food, transit, home). So, she can’t immediately start making loan payments. She sets a goal of making a large payment on her loan after saving up for 11 years. 
a) How much will she owe after 11 years? Use the sketch tool to show your work.
b) How many times higher is the amount she owes after 11 years, compared to the original amount?
c) Imagine Sarah now makes a large loan payment of $31,501. How much does she owe after this payment? d) Imagine Sarah paid the same amount ($31,501) but only 2 years after graduation. How much would she still owe?

1 Answer

2 votes

If Sarah paid the same amount ($31,501) but only 2 years after graduation, she would still owe approximately $26,011.12.

a) To calculate the amount Sarah will owe after 11 years, we can use the formula for compound interest:

A = P(1 + r/n)^(nt)

Where:

A is the final amount (amount owed after 11 years),

P is the principal amount (original loan amount),

r is the annual interest rate (as a decimal),

n is the number of times interest is compounded per year, and

t is the number of years.

Given:

P = $38,876

r = 6.6% = 0.066 (as a decimal)

n = 1 (compounded annually)

t = 11 years

Substituting the values into the formula:

A = $38,876(1 + 0.066/1)^(1*11)

A ≈ $38,876(1.066)^11

A ≈ $38,876(1.8388)

A ≈ $71,470.59

Sarah will owe approximately $71,470.59 after 11 years.

b) To calculate how many times higher the amount she owes after 11 years is compared to the original amount, we can divide the final amount by the principal amount:

Times Higher = A / P

Times Higher = $71,470.59 / $38,876

Times Higher ≈ 1.839

Therefore, the amount she owes after 11 years is approximately 1.839 times higher than the original amount.

c) If Sarah makes a large loan payment of $31,501, we can subtract this payment from the amount she owes after 11 years:

Amount Owed = $71,470.59 - $31,501

Amount Owed ≈ $39,969.59

Therefore, after making a payment of $31,501, Sarah will owe approximately $39,969.59.

d) If Sarah paid the same amount ($31,501) but only 2 years after graduation, we need to calculate the interest accumulated during those 2 years and subtract it from the payment amount. Let's calculate the interest first:

Interest = P(1 + r/n)^(nt) - P

Interest = $38,876(1 + 0.066/1)^(1*2) - $38,876

Interest ≈ $38,876(1.1388) - $38,876

Interest ≈ $44,365.88 - $38,876

Interest ≈ $5,489.88

Now, subtract the interest from the payment amount:

Amount Owed = $31,501 - $5,489.88

Amount Owed ≈ $26,011.12

If Sarah paid the same amount ($31,501) but only 2 years after graduation, she would still owe approximately $26,011.12.

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