subtracting two numbers, one of which is greater than 9 and the other less. You should write down a great number of such sentences as the following, which will exercise you at the same time in addition, and in the use of the signs mentioned in
| 12 + 6 = 18 | 22 + 6 = 28 | 19 + 8 = 27 | |
|---|---|---|---|
| 54 + 9 = 63 | 56 + 7 = 63 | 22 + 8 = 30 | |
| 100 - 9 = 91 | 27 - 8 = 19 | 44 - 6 = 38, | &c. |
- When the last two articles have been thoroughly studied, you will be able to find the sum of any numbers by the following process,1 which is the same as that in (29).
Rule I. Place the numbers under one another, units under units, tens under tens, and so on.
II. Add together the units of all, and part the whole number thus obtained into units and tens. Thus, if 85 be the number, part it into 8 tens and 5 units; if 136 be the number, part it into 13 tens and 6 units (20).
III. Write down the units of this number under the units of the rest, and keep in memory the number of tens.
IV. Add together all the numbers in the column of tens, remembering to take in (or carry, as it is called) the tens which you were told to recollect in III., and divide this number of tens into tens and hundreds. Thus, if 335 tens be the number obtained, part this into 33 hundreds and 5 tens.
V. Place the number of tens under the tens, and remember the number of hundreds.
VI. Proceed in this way through every column, and at the last column, instead of separating the number you obtain into two parts, write it all down before the rest.
Example.—What is
1805 + 36 + 19727 + 3 + 1474 + 2008
- 1805
- 36
- 19727
- 3
- 1474
- 2008
- ——-
- 25053
The addition of the units’ line, or 8 + 4 + 3 + 7 + 6 + 5, gives 33, that is, 3 tens and 3 units. Put 3 in the units’ place, and add together the line of tens, taking in at the beginning the 3 tens which were created by the addition of the units’ line. That is, find 3 + 0 + 7 + 2 + 3 + 0, which gives 15 for the number of tens; that is, 1 hundred and 5 tens. Add the line of hundreds together, taking care to add the 1 hundred which arose in the addition of the line of tens; that is, find 1 + 0 + 4 + 7 + 8, which gives exactly 20 hundreds, or 2 thousands and no hundreds. Put a cipher in the hundreds’ place (because, if you do not, the next figure will be taken for