CASE IV. When the time is years and parts, and the rate per cent has also fractional parts. Proceed with the time as in Case III, then multiply by the integer of the rate, and take parts for the fractional parts. EXAMPLES. 1. What is the interest 2. What is the interest of $963,11, for 7 years of £57 8 44, for 3 years, and 10 months, at 52 per 4 months, and 25 days, at cent. per annum ? 64 per cent. per annum ? 4 months are 6 months are 4 months 537 8 4 13 963,11 3 The following rule for calculating interest is inserted to accommodate those who may prefer it.' To find the interest of any sum, for any number of months, at any rate per cent. * In taking parts of a month for the days, the month is here called 30 days. RULE. Multiply the principal by the number of months, divide the product by the number in the following table,* answering to the rate per cent. Point off the right hand figures, as in the other method. 1. Required the interest of $500 for 16 months, at per cent. 500 16 6)8000 Ans. $13,33,3 2. Required the interest of $1000 for 10 months, at 3 per cent. Ans. $25. 3. Required the interest of $936 for 17 months, at 4 per cent. Ans. $53,04. 4. Required the interest of $1173,57, for 18 months, at 5 per cent. Ans. 888,01,44. 5. Required the interest of £1136 16 8, for 21 months, at 6 per cent. Ans. 119 7 420. CASE V. When the given time is weeks only. Find the interest for a year by Case I, then multiply the year's interest by the number of weeks, and divide by 52. * These divisors are found by dividing 12 (the months in a year) by the rate per cent, and may be found for any rate per cent. CASE VI. When the given time is days only. Multiply the principal by the days, and that product by the rate per cent.; then divide this second product by 36525*. * 36500 is used by most writers on this method, on a supposi. tion, that 365 days make one complete year; but as the year is nearly 3651 days, instead of annexing two ciphers to the 365, I annex,25, which makes it 36525, and gives the interest nearer the truth, than 36500 will. 3. What is the interest of 256 dols. from June 1, to Sept. 10, inclusive, at 6 per cent. per annum? Ans. dolls. 4,28,9+ When partial payments have been made, in order to find what is due, proceed as follows, viz. Compute the interest from the time it commences, to the time the payment is made, which including all previous payments, (if any) exceeds the interest then due; add this interest to the first principal, and from the amount subtract the payment (or sum of payments) to that time; the remainder will be a new principal, for which compute and subtract as before, &c.* This has been practised in the Massachusetts courts of law, as an established rule. |