about interest

[$200000 * (1+0.24/12) - $10000] * (1+0.24/12) - $10000
=$187880

My answer will be the same as the above. But just a bit different.

FOR MONTH-END INSTALLMENTS:

Assume we borrowed $200,000 at 1 Jan 2006
and we pay the first installment at 31 Jan 2006

Principal is $200,000
Annual rate=24%

So, monthly rate is 24%/12=2%

Outstanding balance after 1st month: (at 31 Jan 2006)
$200,000*(1+2%)=$204,000

But we repay $10,000, so $204,000-$10,000=$194,000 (at 1 Feb 2006)

And...

Outstanding balance after 2nd month: (at 28 Feb 2006)
$194,000*(1+2%)=$197,800

But we repay $10,000, so $197,800-$10,000=$187,800 (at 1 March 2006)
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If, it is month-start installments, then the answer is...

FOR MONTH-START INSTALLMENTS

Principal is $200,000
Annual rate=24%

So, monthly rate is 24%/12=2%

Assume we borrowed $200,000 at 1 Jan 2006
and we pay the first installment at 1 Jan 2006
(eg: 有時有d 分期付款買野. 一買就要俾第一期先)

so, outstanding balance is $200,000-$100,00 = $190,000 (at 1 jan 2006)

Outstanding balance after 1st month: (at 31 jan 2006)
$190,000*(1+2%)=$193,800

at beginning of the feb, we repay $10,000, so $193,800-$10,000=$183,800 (at 1 feb 2006)

And...

Outstanding balance after 2nd month: (at
$183,800*(1+2%)=$187,476

at 1 march, we repay $10,000, so $187,476-$10,000=$177,476

Monthly instalment = $10,000
Annum interest rate = 24%, Monthly interest rate = 2%
Principal = $200,000
Interest in first instalment = $200,000 x 2% = $4,000
Principal repaid in first instalment =$10,000 -$4,000=$6,000
Outstanding balance after first instalment = $194,000
Interest in second instalment = $194,000 x 2% = $3,880
Principal repaid in second instalment =$10,000 -$3,880=$6,120
Therefore, outstanding balance after paying two month-end installments = $194,000 - $6,120 = $187,880