Im having trouble coming up with a formula for principle portion of last loan payment. I Already came up with the formulas for monthly, first payment, the total cost of the loan.

**interest 7.75% d4**

amortization period in years 18 d5

Principle amount to be borrowed $1,750,000 d6

monthly loan payment $15,048.32

Principle portion of the first loan payment $3,746.24

**Principle portion of the last loan payment $?? here's what i came up with so far =PPMT(d4/12,1,d5*12,d6,0)**

Total cost of loan $3.250,437.08

You correctly wrote -PPMT(D4/12,

**1**,D5*12,D6) for the first principal payment.

The last principal payment is -PPMT(D4/12,

**D5*12**,D5*12,D6).

I understand that your homework assignment requires that you use PPMT. But that is not a good choice.

In the real world, payments must be rounded to the cent, at least. So the actual payment is =-

**ROUND(**PMT(D4/12,D5*12,D6)

**,2)**.

That looks the same when formatted with 2 decimal places, namely 15,048.32. But without rounding, -PMT(D4/12,D5*12,D6) actually returns about 15048.3198120013.

Consequently, -PPMT(D4/12,D5*12,D5*12,D6) returns about 14951.7563853459, which is displayed as -14951.

**76** when formatted with 2 decimal places.

But the actual last principal amount is the balance after the last-minus-one payment, namely:

=ROUND(FV(D4/12,D5*12-1,ROUND(PMT(D4/12,D5*12,D6),2),D6),2)

which returns -14951.

**67**. (Dyslexia alert! :->)

Similarly, the total cost of the loan is:

=-ROUND(PMT(D4/12,D5*12,D6),2)*D5*12

which is 3,250,437.

**12**, not 3,250,437.

**08** when formatted with 2 decimal places.

That said, you should give your teacher the answer that he/she expects.

Or be a mensh and provide both sets of answers with some explanation. It might earn you some extra points.