4. Find the interest on £955 : 10 : 6 for 6 years 275 days at 5} per cent. £955 : 10 : 6 = £955.525. } X 275 days = 55 days X 5 = .056. 955.525£ = Principal .056 = Int. of £1 73)2943.017000 ( 40.3153£ = Int. for 275 days 321.0564£ = Int. for 6 years 5. Find the interest on £1056 : 15: 6 for 2 years 89 days at 34 per cent. £1056 : 15:6 = £1056.775 – Principal .0325 Int. of £l for 1 year 6. Find the interest on £10765 : 10:0 for 25 years 333 days at 4 per cent. £10765: 10:0 = £10765.5 = Principal .04 = Int. of £1 430.620 = Int. of Principal for 1 year 3 X 333 = 66.6 7. The same example worked by the short rule for division by 73. £10765 : 10:0 = £10763.5 = Principal .04 = Int. of £1 430.620 = Int. of Principal for 1 year 3 X 333 66.6 £392.8663 = Int. for 333 days £10765.5 = Int. for 25 years £11158.3663 = Int. for 25 years 333 days Ans. £11158: 7: 4. 8. A bill of £2000 became due on March 31, of which £500 was paid on May 25, £700 on July 31, £500 on Sept. 30, and the balance on Dec. 31; how much interest was then due at 4 per cent? and what was the last payment? £. products March 31 Due 2000 X 55 = 110000 May 25 Paid 500 Bal. 1500 X 67 = 100500 July 31 Bal. 800 X 61 = 48800 Sept. 30 Bal. 300 X 92 = 27600 286900 Sum of products 9. Required the interest on the following account current, up to Dec. 31, at 41 per cent. Dr. John Cole in account current with Richard Owen. Cr. £ £. July 31 By cash 300 Sept. 25 By goods 450 Nov. 30 By cash 500 150 £. Cr. June 24 To 560 X 190 = 106400 July 31 By 300 X 153 = 45900 Aug. 25 To 360 X 128 = 46080 Sept. 25 By 450 X 97 43650 Sept. 29 To 200 x 93 = 18600 Nov. 30 By 500 X 31 = 15500 Nov. 30 To 150 X 31 = 4650 TO FIND THE AMOUNT OF A GIVEN SUM AT A GIVEN RATE FOR A GIVEN TIME. Rule. Calculate the interest by the preceding Rule, and add to it the principal. 111. TO FIND THE TIME IN WHICH THE INTEREST ON A GIVEN PRINCIPAL WILL AMOUNT TO A GIVEN SUM. Rule. Calculate the interest for 1 year, and find the ratio of the given interest to this; the result will be the number of years required. If the amount be given, instead of the interest, subtract the principal, thus obtaining the interest, and proceed as before. EXAMPLE. Find the time in which the interest on £750 : 10:0 will amount to £712 : 19:6 at 4 per cent. £750 : 10:0 = £750.5 = Principal 37525 52535 30020 35.64875 = Int. for 1 year. .. No. of years = 20. IV. TO FIND THE RATE PER CENT. AT WHICH THE INTEREST ON A GIVEN PRINCIPAL WILL AMOUNT TO A GIVEN SUM IN A GIVEN TIME. Rule. Calculate the interest for the given time at 1 per cent. and find the ratio of the given interest to this; the result will be the rate required. If the amount be given, instead of the interest, subtract the principal, so obtaining the interest, and proceed as before. EXAMPLE. £ 1132.5 = Amount. Int. at 1 per cent. = £7.55 X 10 = £75.5 £377.5 = Interest. 377.5 = 5. Ans. 5 per cent. 75.5 V. TO FIND WHAT PRINCIPAL WILL AMOUNT TO A GIVEN SUM AT A GIVEN RATE IN A GIVEN TIME, OR TO FIND THE PRESENT WORTH OF A GIVEN SUM. Rule. Calculate the amount of £1 for the given time at the given rate, and find the ratio of the given amount to this; the result will be the principal required in pounds. If the interest be given, find the interest on £1, and proceed as before. |