Again, suppose it required to find what part of a pound 6s. 8d. is. Since 6s. 8d. is 80 pence, and since the whole pound contains 20 × 12 or 240 pence, 6s. 8d. is made by dividing the pound into 240 parts, and taking 80 of them. It is therefore £⁸⁰/₂₄₀ (107), but ⁸⁰/₂₄₀ = ⅓ (108); therefore, 6s. 8d. = £⅓.
EXERCISES.
| ⅖ of a day is | 9ʰ 36ᵐ |
| ·12841 of a day | 3ʰ 4ᵐ 54ᔆ·624[45] |
| ·257 of a cwt. | 28ˡᵇˢ 12ᵒᶻ 8ᵈʳ·704 |
| £·14936 | 2ˢ 11ᵈ 3ᶠ·3856 |
221, 222. I have thought it best to refer the mode of converting shillings, pence, and farthings into decimals of a pound to the Appendix ([See Appendix On Decimal Money]). I should strongly recommend the reader to make himself perfectly familiar with the modes given in that Appendix. To prevent the subsequent sections from being altered in their numbering, I have numbered this paragraph as above.
223. The rule of addition[46] of two compound quantities of the same sort will be evident from the following example. Suppose it required to add £192. 14. 2½ to £64. 13. 11¾. The sum of these two is the whole of that which arises from adding their several parts. Now
| ¾d. + ½d. | = | ⁵/₄d. | = | £0 . 0 . 1¼ | (219) |
| 11d. + 2d. | = | 13d. | = | 0 . 1 . 1 | |
| 13s. + 14s. | = | 27s. | = | 1 . 7 . 0 | |
| £64 + £192 | = | = | 256 . 0 . 0 | ||
| The sum of all of which is | £257. 8 . 2¼ | ||||
This may be done at once, and written as follows:
- £192.14. 2½
- 64.13.11¾
- £257. 8. 2¼
Begin by adding together the farthings, and reduce the result to pence and farthings. Set down the last only, carry the first to the line of pence, and add the pence in both lines to it. Reduce the sum to shillings and pence; set down the last only, and carry the first to the line of shillings, and so on. The same method must be followed when the quantities are of any other sort; and if the tables be kept in memory, the process will be easy.
224. Subtraction is performed on the same principle as in (40), namely, that the difference of two quantities is not altered by adding the same quantity to both. Suppose it required to subtract £19 . 13. 10¾ from £24. 5. 7½. Write these quantities under one another thus: