jch103020
Bunuel
A loan has a variable interest rate that fluctuates between 5% and 9% of the base payment per month. If base payments remain at $250 each month and an additional monthly surcharge of 1% is added to the combined (base + interest), what would be the greatest possible payment due in any given month?
A. $262.50
B. $265.13
C. $272.50
D. $275.23
E. $286.13
Can someone explain this one to me using a different method or point out the error in my thinking?
Use max value of 9% interest to calculate base and then add 1% interest to that value
Base payment + Base interest + Additional interest = Total
250 + .09(250) + (.01(.09(250)) =250 + 22.5 + .225 = 272.725
jch103020 , easy mistake.
The "additional interest" does not work because you are charging 1% on
interest only:
(.09)(250) = $22.50, and
($22.50 *.01) = $0.225
The extra 1% should be charged on
base + interest: 1.09(250) = $272.50
So either
Base payment + Base interest + Additional interest (
1% on base payment PLUS base interest) = Total
250 + .09(250) + (.01*
(1.09*(250)) = (250 + 22.5 + 2.725) = $275.225
OR
Add your first two terms:
$250 + $22.50 = $272.50
1% on that amount: (.01)($272.5) = $2.725
Add that amount to your "running total":
($250 + $22.50 + $2.725) = $275.225
If you think about multiplying decimals, it makes sense. (.01*.09) = .0009. You've charged 9/100th of a percent (.09%) on $250
Hope that helps.