
Steve B. answered 06/02/22
Degree in Finance, father of four, financial analyst for 10+ years
a.) We have a $51,000 loan with an interest rate of .0468 compounded quarterly for the first 6 months. Ok, 6 months is half a year. Quarterly is 1/4 of a year or every 3 months, so for the first 6 months we're going to compound (add up the interest to the balance and take that new bigger balance to charge interest on) our loan twice.
The first 6 months are compounded Quarterly, or every 3 months at a 4.68% interest rate.
The first 3 months we'd take (51,000 x .0468) + 51,000 = $53,386.80
The next 3 months we'd use our new balance of (53,386.8 x .0468) + 53,386.8 = $55,885.30
b.) The next two years (24 months) are compounded semi annually (twice a year or every 6 months) at a 5.55% rate.
So we know during that two year period we're going to compound the interest on our loan twice a year or 4 times over that period. We take the balance we got from A and use it to start our calculations on B.,
The first 6 months would be ($55,885.3 x 5.5%) + $55,885.3 or $58,958.99
The next 6 months would be ($58,958.99 x .055) + $58,958.99 or $62,201.73
We would then do that two more times to find the balance at the end of the two year period of 5.5% interest compounded semiannually.
c.) The loan was take out 7 years ago. We've calculated 6 months plus another 24 months, or 30 months total so far. 7 years is 84 months (7x12), so we have 54 months (84-30) of interest left to calculate at a monthly compounded rate of 5.67%
At this point we could take our balance of $62,201.73, multiply it by .0567, add it to the previous balance and do it again 53 more times or we could use a formula. I vote formula.
Total = Principal(1 + interest rate/ number of times compounding yearly)^number of years.
In our case: T = $62,201.73[(1 + .0567)/12]^4.42 (4.42 comes from 53 months remaining/ 12 months in a year to get 4.4166666 years left)
PEMDAS says do parenthesis first, then exponents, so lets simplify it a bit:
T= $62,201.73(1.0567)^4.42
T= $62,201.73 times 1.276
T= $79,369.41
d.) Now we just go back through and add up all the interest over the past 7 year