55. What is the interest of $47,50 for 1 year, 7 months, and 13 days, at 7 per cent.?

47.50

I first find the interest for 1 year, and then of that is the interest for 6 months; of the interest for 6 months will be the interest for 1 month; of the interest for 1 month will be the interest for 10 days, and of the interest for 10 days is very near the interest for 3 days. All these added together will give the interest for the whole time. In a similar manner, the interest for any time at any rate per cent. may be calculated.

When there are months and days, it is better to calculate the interest first at 6 or 12 per cent., and then change it to the rate required. Observe that 1 per cent. is of 6 per cent., 11 per cent. is of 6 per cent., 2 per cent is of 6 per cent, &c. Hence if the rate is 7 per cent., calculate first at 6 per cent., and then add of it to itself, or if 5 per cent., subtract; if 7 or 4 per cent. add or subtract 4, &c. Let us take the above example.

6 per cent. for 1 year, 7 months, and 13 days, is 97 per cent. nearly, that is .097.

This answer agrees with the other within about 1 cent. Greater accuracy might be attained, by carrying the rate to one or two more decimal places.

56. What is the interest of $135.16 from the 4th June, 1817 to 13th April, 1818, at 5 per cent. ?

57. What is the interest of $85.37 from 13th July, 1815, to 17th Nov. 1818, at 4 per cent.?

58. What is the interest of $45.87 from 19th Sept. 1819, to 11th Aug. 1821, at 7 per cent. ?

59. What is the interest of $183 from 23d Oct. 1817, to 19th Jan. 1820, at 4 per cent. ?

60. What is the interest of 113£. 14s. for 1 year, 5 months, and 8 days, at 7 per cent. ?

61. What is the interest of 87£. 15s. 4d. for 2 years, 11 months, 3 days, at 7 per cent. ?

62. What is the interest of 43£. 16s. for 9 months and 13 days, at 8 per cent. ?

63. What is the interest of 142£. 19s. for 1 year, 8 months, and 13 days, at 9 per cent. ?

64. What is the interest of $372 for 4 years, 8 months, and 17 days, at 74 per cent.?

65. What is the interest of 1 dollar for 15 days at 7 per cent. ?

66. What is the interest of $.25 for 13 days, at 7 per cent. ? 67. What is the interest of $.375 for 19 days, at 11 per

cent. ?

68. What is the interest of $1147 for 8 hours, at 6 per cent.?

69. What is the interest of 137£. 11s. for 11 days at 9 per cent. ?

70. What is the interest of 15s. for 3 months, at 8 per cent. ?

71. What is the interest of 16£. 7s. 8d. for 2 months, at 12 per cent. ?

72. What is the interest of 4s. 3d. for 17 years, 3 months, and 7 days, at 8 per cent. ?

73. A man gave a note 13th Feb. 1817, for $753, interest at 6 per cent., and paid on it as follows: 19th. Aug. 1817, $45; 27th June, 1818, $143; 19th Dec. 1818, $25; 11th May 1919, $100; and 14th Sept. 1820, he paid the rest, principal and interest. How much was the last payment ?

74. A note was given 17th July, 1814, for $1432, interest at 6 per cent., and payments were made as follows; 15th Sept. same year, $150; 2d Jan. 1815, $130; 16th. Nov. 1815, $23; 11th April, 1817, $237; 15th Aug. 1818, $47. How much was due on the note, principal and interest, 5th Feb. 1819?

ARITHMETIC.

PART II.

NUMERATION.

I. A single thing of any kind is called a unit or unity. Particular names are given to the different collections of units.

A single unit is called

one are

are

One.

Four.

Five.

Six.

Seven.

If to one unit we join one unit more, the collection is called two; that is, one added to one is called two, or one and Two. One added to two is called three; two and one are Three. One added three is called four; three and one are One added to four is called five; four and one are One added to five is called six; five and one are One added to six is called seven; six and one are One added to seven is called eight; seven and one Eight. One added to eight is called nine; eight and one are Nine. One added to nine is called ten; nine and one are Ten. In this manner we might continue to add units, and to give a name to each different collection. But it is easy to perceive that, if it were continued to a great extent, it would be absolutely impossible to remember the different names; and it would also be impossible to perform operations on large numbers. Besides, we must necessarily stop somewhere; and at whatever number we stop, it would still be possible to add more; and should we ever have occasion to do so, we should be obliged to invent new names for them, and to explain them to others. To avoid these inconveniences, a method has been contrived to express all the numbers, that are necessary to be used, with very few names.

The first ten numbers have each a distinct name. The collection of ten simple units is then considered a unit: it is called a unit of the second order. We speak of the collections of ten, in the same manner that we speak of simple units; thus we say one ten, two tens, three tens, four tens, five tens, six tens, seven tens, eight tens, nine tens. These expressions are usually contracted; and instead of them we say ten, twenty, thirty, forty, fifty, sixty, seventy, eighty, ninety.

The numbers between the tens are expressed by adding the numbers below ten to the tens. One added to ten is called ten and one; two added to ten is called ten and two; three added to ten is called ten and three, &c. These are contracted in common language; instead of saying ten and three, ten and four, &c., we say thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, nineteen. These names seem to have been formed from three and ten, four and ten, &c. rather than from ten and three, ten and four, &c., the number which is added to ten being expressed first. The signification, however, is the same. The names eleven and twelve, seem not to have been derived from one and ten, two and ten; although twelve seems to bear some analogy to two. The names oneteen, twoteen, would have been more expressive; and perhaps all the numbers from ten to twenty would be better expressed by saying ten one, ten two, ten three, &c.

The numbers between twenty and thirty, and between thirty and forty, &c. are expressed by adding the numbers below ten to these numbers; thus one added to twenty is called twenty-one, two added to twenty is called twenty-two, &c.; one added to thirty is called thirty-one, two added to thirty is called thirty-two, &c.; and in the same manner forty-one, forty-two, fifty-one, fifty-two, &c. All the numbers are expressed in this way as far as ninety-nine, that is nine tens and nine units.

If one be added to ninety-nine, we have ten tens. We then put the ten tens together as we did the ten units, and this collection we call a unit of the third order, and give it a name. It is called one hundred.

We say one hundred, two hundreds, &c. to nine hundreds, in the same manner, as we say one, two, three, &c.

The numbers between the hundreds are expressed by adding tens and units. With units, tens, and hundreds we

can express nine hundreds, nine tens, and nine units; which is called nine hundred and ninety-nine. If one unit be added to this number, we have a collection of ten hundreds; this is also made a unit, which is called a unit of the fourth order; and has a name. The name is thousand.

This principle, may be continued to any extent. Every collection of ten units of one order is made a unit of a higher order; and the intermediate numbers are expressed by the units of the inferior orders. Hence it appears that a very few names serve to express all the different numbers which we ever have occasion to use. To express all the numbers from one to nine thousand, nine hundred, and ninety-nine, requires, properly speaking, but twelve different names. will be shown hereafter, that these twelve names express the numbers a great deal farther.

It

Various methods have been invented for writing numbers, which are more expeditious, than that of writing their names at length, and which, at the same time, facilitate the processes of calculation. Of these the most remarkable is the one in common use, in which the numbers are expressed by characters called figures. This method is so perfect, that no better can be expected or even desired. These figures

are supposed to have been invented by the Arabs; hence they are sometimes called Arabic figures. The figures are nine in number. They are exactly accommodated to the manner of naming numbers explained above.*

Next to the Arabic figures, the Roman method seems to be the most convenient and the most simple. It is very nearly accommodated to the mode of naming numbers explained above. A short description of it may be interesting to some; and it will often be found extremely useful to explain this method to the pupil before the other. The pupil will understand the principles of this, sooner than of the other, and having learned this, he will more easily comprehend the other. He will perfectly comprehend the principle of carrying, in this, both in addition and subtraction, and the similarity of this to the common method is so striking that he will readily understand that also. The pupil may perform some of the examples in Sects. I, II, and VIII, Part I, with Roman characters.