Hi SwethaReddyL,Great question, and it's exactly the spot where real-life loan intuition fights the wording of this problem.
In a normal loan, you'd be right: after paying back part of the principal, interest would drop because it's charged on what's
still owed. But this question deliberately overrides that. Look at the exact words:
"the moneylender charged an interest equal to
5 percent per quarter on the original loan amount."
The phrase
"on the original loan amount" is the whole key. The interest is always
5% of
$2000 =
$100 per quarter, and it keeps being charged that way until the principal is
completely gone - no matter how much principal Ricky has already paid back.
So in stne's solution, the interest never shrinks. That's why:
- Principal repaid per half-year =
$100, so paying off
$2000 takes
20 half-years =
40 quarters.
- Interest =
$100 every quarter for all
40 quarters =
$4000.
- Total = principal
$2000 + interest
$4000 =
$6000 - answer
B.
If the interest
had been on the remaining balance, the total would be smaller - but the question locks it to the original
$2000, so it stays a flat
$100 each quarter.
Quick way to feel the difference: imagine a
$100 loan where you repay
$10 principal each period and interest is "
5% per period on the original amount." Interest is
$5 every period the whole time - it does
not drop to
5% of
$90, then
5% of
$80, and so on. Whenever a problem says "on the original amount," treat that base as frozen.
Answer: BSwethaReddyL
this is a bit confusing; after paying back first portion of his principal, will the interest be on the remaining amount or the original amount?