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# Interesting Calculations

June 02, 1996|KATHY M. KRISTOF

With a standard calculator, you have to compute interest for each year successively. It's much faster to use a present-value calculator, which has special keys to speed the process.

You can usually use such calculators to solve other problems with statistics, annuities and mortgages. (One basic present-value calculator is the Texas Instruments BA-35, which retails for about \$20 at discount office stores.)

To illustrate, consider someone who wants to know what they'd end up with from a five-year certificate of deposit, yielding 5.71% annually, if they deposited \$10,000 and didn't take any withdrawals of principal or interest.

On a present-value calculator, you would punch in:

* 10,000, then hit "pv" for the present value of the account

* 5.71, then "%i" for the interest rate

* 5, then "n" for the number of periods (in this case, years)

* 0, then "pmt" for payment (in this case, you are not adding to the account during the period)

* "cpt, fv" for compute future value. The result: \$13,200.

An alternative is to use a compound interest table, found in some financial books or sold in office supply stores. Also, for \$8.75, Joe Mintz sells one that you can use to find a simple multiplier for interest rates ranging between 4% and 9.9% and terms stretching to 50 years. Those who want to buy his Instant Yield Calculator should send a check or money order to Yield-Department L, P.O. Box 12066, Dallas, TX 75225.