Section 10. COMPOUND SUBTRACTION. COMPOUND SUBTRACTION teaches to find the difference between two numbers of different denominations. 1. A bill on the bank of England for £713. 17s. 11d. 3qr. was sold for £765. 16s. 10d. 1qr.; what was the sum gained? Ans. £51. 18s. 10d. 2qr. penny 4qr., which we add to the 1qr.5qr. Take 3qr. from 5qr., and 2qr. remain, which we write under the column of farthings; and, as in simple numbers, we carry one to the next lower number before subtracting. And 1d. carried to 11d. is 12d. ; but, as we cannot take 12d. from 10d., we must again borrow 1s. from the 16s. 12d. and add it to the 10d. 22d. Then take 12d. from 22d. = 10d., which we set down and carry one, as before, and so on till the whole be subtracted. Hence the following RULE. Write those numbers under each other, which are of the same denomination, the less compound number under the greater. Begin with the lowest denomination, and subtract each lower number from the one above it, and write the difference underneath. If any lower number be larger than the upper, suppose as many to be added to the upper number as would make one of the next higher denomination, then subtract the lower figure, remembering to carry one to the next lower number before subtracting it; and proceed thus, till all the numbers are subtracted. 2. From £87. 11s. 9d. 3qr. take £41. 5s. 6d. 1qr. Ans. £46. 6s. 3d. 2qr. EXERCISES IN COMPOUND ADDITION AND SUBTRACTION. 1. What is the amount of the following quantities of gold; 4lb. 8oz. 13dwt. 8gr., 5lb. 11oz. 19dwt. 23gr., 8lb. Ooz. 17dwt. 15gr., and 18lb. 9oz. 14dwt. 10gr. ? Ans. 37lb. 7oz. 5dwt. 8gr. 2. An apothecary would mix 7b. 33. 23. 29. 1gr. of rhubarb, 2b. 103. 03. 19. 13gr. of cantharides, and 2lb. 33.73. 29. 17gr. of opium; what is the amount of the compound? Ans. 12b. 53. 33. 09. 11gr. 3. Add together 17T. 11cwt. 3qr. 11lb. 12oz., 11T. 17cwt. 1qr. 191b. 11oz., 53T. 19cwt. 1qr. 17lb. 8oz., 27T. 19cwt. 3qr. 18lb. 9oz., and 16T. 3cwt. 3qr. Olb. 13oz. Ans. 127T. 12cwt. Iqr. 12lb. 5oz. E |