Page:Methods of Operating the Comptometer (1895).djvu/35



Multiply the principal in cents by the rate of interest and add the principal. Set the amount down on paper in dollars and cents, leaving off the mills and tens of mills, and begin on the unit key of the row of keys representing the rate per cent., and without turning the machine to naught, multiply the amount set down by the rate per cent., thereby placing the product two places to the right of the amount standing on the machine. Set down on paper the amout now on the machine, which is the amount of compound interest and principal for two years. Proceed in like manner, as many times as there are years remaining in the term for which the interest is to be compounded.

What is the amount of $326.21 for five years at 7 per cent. compound interest?

Starting on the row of 7's indicated by the rate per cent., strike the first one, one time, the next two times, the third six times, and so on. $22.8347 appears on the register, as the interest for one year. Add the principal and $349.04 appears as the amount of interest and principal for one year, the mills and tenths of mills being disregarded. Starting on the row of 7's, strike the first 7 four times, the third nine times, the fourth four times, and the fifth three times. The amount of interest and principal will now be indicated on the register. Setting this down, continue the operation as directed by above rule, three times more, when the amount of compound interest and principal for five years will be indicated on the register.