| 320,012 |
| 199,999 |
| ——— |
| 120,013 |
Now, you cannot take 9 from 2, so you “borrow” one from the left and make your two 12. Then 9 from 12 leaves 3. In borrowing from the left you reduce the 1 in the tens column to 0. As you cannot take 9 from 0, you must again borrow from the left. But what are you to borrow from? In the third, or hundreds column there is only a 0. Hence, before you can borrow from this column you must make this 0 a 10 by borrowing from the fourth, or thousands column (counting your columns always from the right).
But again here you find only a 0, and so before you can make even this “borrow” you must borrow one from the 2 in the ten thousands column. Now see what happens. With the one which you have finally borrowed you have made the 0 left in the second or tens column into a 10, and you take 9 from 10, which leaves 1.
Now, here is where you forget something. When you started out to “borrow” you had to go away over to the 2 in the fifth column; that made your 0 in the fourth column a 10, but you immediately passed this one on to the third column, which left only 9; again you passed it on from the third to the second column, which left only a 9 in the third column. Hence you have now a 9 in the third and in the fourth columns, and your results there will be in each case 9 from 9 leaves 0.
Coming to the fifth you have a 1 instead of a 2, having borrowed 1; and you have to borrow again from the 3 to make your 1 into an 11, obtaining 9 from 11 leaves 2; and your sixth and last figure, being reduced from 3 to 2, your last result is 1 from 2 leaves 1.
This last part is easy, but one out of practice is almost certain to forget that his 0’s in the third and fourth columns became 9’s. If you have any difficulty with subtraction, study out the processes in this example until you understand them and you will never make a mistake again.
Now, as to the shape in which the examples will be given: The plain problems in addition will be unmistakable. You will be told that a concern sold 27,356 barrels of flour in one month, 38,452 the next, etc., and you cannot well run off the track. But you may find both processes involved in one “problem,” and you must then be careful to understand just what is meant by the question, so that you will know what you are expected to do with the figures.
Take this, for example: “A had $3,465 and B $4,895. A gained $1,146 and B lost $602. Which then had the more, and how much?”
Here you must add A’s gain to his principal—that is, the sum he had to start with—and subtract B’s loss from his principal; then subtract the smaller result from the larger, stating which is the “winner.” Thus: