Calculate the interest on the following sums at £5 per To find the interest for months at £6 per cent. : RULE.-Divide the principal in pounds, by 5, the quotient considered as sixpences, will be the interest for 1 month, at £6 per cent, which multiply by the number of months, and the product will be the interest for the required time. The reason of this is, that as 1d. is the interest of £1 for 1 month, at £5 per cent. per annum; so the interest of £1 for 1 month, at £6 per cent. per annum must be 1d.; and, therefore, the interest of £5, at the same rate and for the same time, must be 6d., hence dividing the principal by 5 must give the interest of that sum for 1 month in sixpences. The reason for the following Rules for the finding of interest is similar to those given. EXAMPLES. Required the interest of £320 12s. 6d. for 4 months at £6 Required the interest of £120 for 3 months at £6 per cen? Required the interest of £145, 17s. 6d. for 6 months at £6 per cent.?(17s. 6d. To find the interest of any sum of money for 1 year, at £6 per cent. :-- RULE.-Multiply the principal, in pounds, by 6, and divide by 5, the quotient will be the interest for 1 year in shillings. Or, add to the principal of itself, both taken in pounds, part or parts of a pound, their sum will be the interest of the sum in shillings, for 1 year at £6 per cent. The reason of this is, that the operation is the same as multiplying the principal by 6, the rate per cent., and dividing by 100; which is the usual method. EXAMPLES. Required the interest of £40 for 1 year at £6 per cent. Or, by the rule for finding the interest for months, thus: = £40 5 and 4s. x 12 8 sixpences 4s. = £2 8s. = interest for 1 month, interest for 1 year, as before. Required the interest of £180, 12s. 6d., for 1 year at £6 per cent. ? Ans. £10 16s. 9d. Calculate the interest on the following sums, at £6 per cent. per annum. To find the interest of any sum of money for months at £2 per cent. :— RULE.-Half the principal in pounds, will be the interest, in pence, for 1 month, which multiplied by the given number of months will be the interest for the required time in pence. Or, find the interest at £5 per cent., and take one half of it, the interest for 1 year is half the principal in pounds, part or parts of £1, considered as shillings. The reason of this is, that the operation is the same as that of multiplying the principal by 24, dividing by 100, and then taking such a part or parts of the interest for 1 year, as the months are of 1 year. EXAMPLES. Required the interest of £40, for 3 months, at £21 per cent. ? £ 2)40 S. D. 20d. 1 8 Interest for 1 month at £2 per cent. 3 = Ans, 5 0 Interest for 3 months. Or, £40 for 1 month at £5 per cent. is £0 3 4 3 £40 for 3 months at £5 per cent. is £0 10 0 Required the interest of £120, 10s. for 6 months at £21 per cent.? Required the interest of £430 15s. for 1 year at £2 pe cent. £ S. D. 2)430 15 0 Ans. £215 7 6* Or, 2153s. = £10, 15s. 4 d. Calculate the interest on the following sums at £2 per cent. : £120 for 3 months....... 320 for 4 months.... 190, 10s. for 7 months. 500, 13s. 4d. for 10 months.. 84, 10s. for 1 year....... 180 for 1 year, 4 months... £ To find the interest of any sum of money for months, at 3 per cent : RULE. Divide the principal in pounds by 20, "the quotient will be the interest in shillings for one month; or, consider the principal in pounds as shillings; these divided by 20, will be the interest of the sum for 1 month, which multiply by the given number of months; or, calculate the interest at £6 per cent., and take one-half of it. To find the interest for 1 year at £3 per cent. :— RULE.-Multiply the principal in pounds by 3, and divide the product by 5, the quotient will be the interest of the sum in shillings. * 7s. 6d. is of £1, and in the answer must be considered as of 18. EXAMPLES. What is the interest of £60 for 3 months at £3 per cent? Required the interest of £180 17s. 6d. for 8 months. at £3 per cent ?-(17s. 6d. Z of £1). Ans. 72s. £3 12s. 4. Interest for 8 mo. = Required the interest of £180 15s. 6d. for 1 year at £3 per cent? (15s. 6d. of £1). = What is the interest of £41 12s. 6d. for 6 months at £3 per cent. ? What is the interest of £80 for 9 months at £3 per cent.? Ans. £1 16s. |