Financial Math Final Flashcards
Simple Interest Formula
I = Pit
Interest charges = PrincipalInterest rate per yearterm of the loan, measured in years
Approximate Time (definition)
Pretend that every month has exactly 30 days
Exact Time (definition)
Find the exact number of days using a serial table which gives numbers to every day of the year
Promissory Note (definition)
document which physically represents a loan
** often SOLD on the basis of DISCOUNT INTEREST, though they usually ACCRUE interest on a Simple Interest basis.
Leap Year (definition)
significant because it means that we’d have to divide the number of days (in exact time) by 366 instead of 365
Future Value (definition)
the amount that money will grow into at some specified point in the future (represented by S)
Simple Interest Factor
(1 + it) – multiplying by this factor moves money forward in time
Future Value formula
S = P(1 + it)
Prompt Payment Discounts (definition)
many contractors offer discounts for early payment of invoices for large amounts of money.
think of paying early as loaning the money to the contractor and the discount as interest earned on that “loan.”
Prompt Payment Discount formula
x/y, n/z = x% discount if paid within the first y days, otherwise the Net amount (n) is due in z days.
Present Value (definition)
the amount of money which must be invested now to grow into a given amount at some point in the future. Represented by “P.”
Present Value Formula
P = S
——-
(1 + it)
“discounting the note” (definition)
this happens when promissory notes (which represent loans) are sold to a third party. The price of the loan is always less than the maturity value.
How to find the discounted note value (“sale price”)
step 1. find the maturity value of the note (future value formula) if not already given.
step 2. find the present value of this maturity value at the sale date (present value formula).
**usually, the interest rates for these 2 steps will be different.
Rate of Return (R.O.R.) formula
i = I d = D 360 (100 - B)
—- ——- d= —— * ————-
Pt St t (B)
*simple *discount disc. for treas. bids
** t meas. in days
(S) i = ------ ^(1/n) - 1 (P) *compound
Focal Date (definition)
In order to reconcile payments and obligations made at different points in time, we have to move all money to a single point in time – the focal date.
“The Golden Rule of Finance” (definition)
monies cannot be added or reconciled unless they are valued at the same point in time.
Net Present Value (definition)
the difference between income and expenses after everything has been moved to the present.
**if we think of expenses as “negative income,” then NPV just means “total present value.”
** depends on interest rate
Internal Rate of Return (I.R.R.) (definition)
the interest rate that makes the net present value come out to ZERO.
Merchant’s Rule (definition)
the maturity date of the loan is used as the focal point. The final payment is equal to the original future value of the loan MINUS the future value of all partial payments.
The United States Rule (definition)
a new computation is done each time a payment is made. We compute the future value of the loan, subtract the payment, and then use the balance as the principle for the new loan.
Annuity (definition)
a sequence of payments made at regular intervals in time
- the payments are usually equal in size
- period of time between payments is called a RENT PERIOD
** if payments of R are made at the end of n consecutive interest periods, we can find the total future value at the day of the final payment
Future Value of an Ordinary Annuity formula
Sn = R * [(1 + i)^n - 1]
—————–
[ i ]
where:
R = rent
n = total # of payments
i = rate per period
Fence Post Principle (definition)
if the problem gives starting and ending dates, and the payments are made at both of these dates, then the total number of payments is ONE MORE than the NUMBER OF INTEREST PERIODS
“a fence of length n has n+1 posts”
Ordinary Annuity (definition)
payments occur at the END of each rent period
Annuity Due (definition)
payments occur at the BEGINNING of each rent period
Present Value of an Annuity (definition)
total present value of all payments one interest period BEFORE first payment (at the beginning of first rent period)
Present Value of an Ordinary Annuity formula
[ 1 - (1 + i)^-n ]
An= R * ——————-
[ i ]
Finding R (formulas)
R = (Sn) / [((1 + i)^n - 1) / i ] R = (An) / [(1 - (1 + i)^-n) / i ]
The Sale Price of an Annuity (definition)
the TOTAL PRESENT VALUE of the remaining payments