Many of the problems we solve are what we refer to as time-value-of-money (TVM) problems, such as finding what a sum of money will grow to, or calculating a monthly payment for a car loan. Three different approaches are used:

Chapters	We use	Calculators that can be used
10 & 11	Formulas	Any calculator that has an exponent (power) key, like ^ or yx
12 & 13	Tables	Any calculator
14,15,19	Financial calculators	HP 10B, HP 10BII, HP 12C, HP 17B, TI BAII PLUS
	Or some graphing calculators	TI 83 PLUS, TI 84 PLUS, Casio 9750G PLUS

Here are a few pros and cons of each method:

Formulas
Using formulas is a fairly straightforward process, although using some of the formulas takes a fair amount of time, and it is easy to make a mistake along the way. Also, there is not a formula that will calculate an interest rate when a periodic payment is involved.

Tables
Tables are very easy to use and give quick results. But the answer is only as precise as the table values (many tables do not show values with an ample number of decimal places). Tables for an unusual interest rate (such as 6.9%) or term (such as 156 months) are not available in most publications, so a precise solution is often not possible with tables. Another drawback is the need to carry a set of tables around. And a big drawback: tables are not designed to solve for i (interest rate) and n (number of periods).

Financial calculators
Using financial calculators gives quick, accurate results to all types of TVM problems. And financial calculators are easy to take anywhere. One drawback: We must buy a calculator (starting at about $35). Another possible drawback: Some people get used to pushing buttons and forget the need for common sense (Garbage In, Garbage Out).

As mentioned above, some graphing calculators can be used to solve TVM problems, although it should be noted that keystrokes for graphing calculators can be quite tedious for many of the applications. Keystrokes for the five financial calculators, 3 graphing calculators, and a few other popular calculators are shown on our Web site; to see keystrokes, click here.