OPERATION. £ S. d. 7 10 18 96 Sum. 18 6 1. 8 9 3 Proof. 18 6 1 Having written down the numbers as the rule directs, begin with the lowest denomination, (pence) and say, 6 to 9 is 15, and 10 is 25. Now since 12d. make a shilling, you must carry by 12; and as there is twice 12 in 25, and 1 over, therefore, set down the 1, and carry 2 to the shillings, and say 2 carried to 8 is 10, and 6 is 16, and 10 is 26, and 10 is 36, and 10 is 46, (the 1's in the second column of shillings being so many tens,) and 20, the number of shillings in a pound, being contained in 46 twice and 6 over, write down the 6, and carry 2 to the pounds, and say, 2 to 7 is 9, and 9 is 18, which write down, and the work is done. The method of proof must be sufficiently obvious from the example and what has been already taught in Simple Addition. 3. Compound Subtraction. COMPOUND SUBTRACTION is the method of finding the difference between numbers which consist of different denominations. Rule.* Write the less number under the greater, so that the parts which are of the same denomination, may stand directly under each other. Begin with the last denomination, and if the lower number exceed the one over it, borrow as many units as will make one of the next higher, and subtract it therefrom; to the difference add the upper number, remembering, when you borrow always to carry one to the next superior denomination in the subtrahend. Proof. The method of proof is the same as in Simple Subtraction. Examples. 1. FEDERAL MONEY. 1. Suppose I lent 3E. 88 7d. 4cts. and received 1E. 89, how much remains due? 1. Suppose I borrowed £149 10s. 8d. and paid £86 12s. 4d. how much remains to be paid? *Borrowing in this rule depends upon the same principle as in Simple Subtraction, and differs from it only on account of the numbers being of different denominations. Hence the reason of the rule must be obvious from what has already been said. |