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To multiply 6 by 10, annex one cipher, thus, 60. On the principle that Division is the reverse of multiplication, to divide 60 by 10, cut off a cipher.
Had the dividend been 65, the 5 might have been separated in like manner as the cipher; 6 being the quotient, 5 the remainder. The same will apply when the divisor is 100, 1000, &c.
Rule for Case II.-Cut off as many figures from the right of the dividend as there are ciphers in the divisor; the figures cut off will be the remainder, the other figures, the quotient. 1. Divide 31872 by 100, OPERATION. 1100348/72
348 Quo. 72 Rem. 2. Divide 2682 by. 10.
Ans. 268 3. Divide 4700 by 100,
Ans. 47. 4. Divide 37201 by 100.
Ans. 372100 5. Divide 46250 by 100.
Ans. 462 600 6. Divide 62034 by 100.
Ans. 620,300 7. Divide 18003 by 1000. 8. Divide 375000 by 1000.
CASE III. Art. 49. To divide, when there are ciphers on the right of the divisor.
1. Divide 4072 by 800. SOLUTION.--Regard 800 as
1100) 40172 a composite number, the fac
8) 40 tors 100 and 8, and divide as
5 Quo. 72 Rem. In dividing by 800, separate the two right hand figo
8,00)40172 ures for the remainder, then
5 Quo. 72 Rem.
in the margin.
divide by 8.
Review.-48. Ilow do you divide by 10, 100, 1000, &c. ? On what principle does the rule for case II depend? 49. How do you divide when there
are ciphers on the right of divisor, Rule for case III ?
2. Divide 77939 by 2400.
SOLUTION.-Since 2400 equals 24100)779 139 (321138 24 X 100, cut off the two right
72 hand figures, the same as divid
59 ing by 100; then divide by 24.
48 Dividing by 100, the remainder is 39; dividing by 24, the remainder is 11. To find
11 the true remainder, multiply 11 by 100, and add 39 to the product, (Art. 47, Rule); this is the same as annexing the figures cut off, to the last remainder. Hence, the
Rule for Case III.--1. Cut off the ciphers at the right of the divisor, and as many figures from the right of the dividend.
2. Divide the remaining figures in the dividend by the remaining figures in the divisor.
3. Annex the figures cut off to the remainder, which gives the
Ans. 223730 7. Divide 907237 by 2100.
Ans. 432. 17
• 8. Divide 364006 by 6400.
Ans. 562906 9. Divide 76546037 by 250000.
350000 10. Divide 43563754 by 63400.
Ans. 687 79.5 4 Exercises in more difficult contractions are in" Ray's Higher Arithmetic.”
PROOF OF MULTIPLICATION BY DIVISION. Art. 50. Division (Art. 37), is a process for finding one of the factors of a product when the other factor is known: therefore,
If the product of two numbers be divided by the multiplier, the quotient will be the multiplicand: Or, if divided by the multiplicand, the quotient will be the multiplier
Review.- 50. What is division ? If the product of two factors be divided by either of them, what will be the quotient?
1. What number multiplied by 7895, will give 434225 for a product ?
Ans. 55. 2. If 327 be multiplied by itself, the product will be 106929. Give the proof.
3. The product is 10741125; the multiplier 375 : what is the multiplicand ?
Ans. 28643. 4. The product is 63550656, and the multiplicand 60352: what is the multiplier ?
Ans. 1053, 1 For additional problems, see Ray's Test Examples.
REVIEW OF PRINCIPLES. ART. 51. NOTATION and NUMERATION show how to express numbers by words, by figures, or by letters.
For other scales of notation than the decimal or tens' scale, an interesting subject for advanced students, see “ Ray's Higher Arithmetic.”
ART. 52. BY ADDITION, The aggregate or sum of two or more numbers is found, (Art. 18). Thus, when the separate cost of several things is given, the entire cost is found by addition.
EXAMPLE.--A bag of coffee cost $23, a chest of tea $38, a box of sugar $11: what did all cost?
Ans. $72. ART. 53. BY SUBTRACTION, The difference between two numbers is found. Thus, if the sum of two numbers be diminished by either of themi, the remainder will be the other.
Hence, by Addition, if the difference of two numbers be added to the less, the sum will be the greater.
Review.--51. What do Notation and Numeration show? 52. What is found by addition? Give an example.
53. What is found by subtraction ? Having the sum of two numbers, and one of them, how is the other found? When the smaller of two numbers and the difference are given, how is the greater found? When the difference and greater are given, how is the less found ?
EXAMPLE 1. The sum of two numbers is 85; the less number is 37: what is the greater ?
2. The sum of two numbers is 85; the greater number is 48; what is the less ?
3. The difference of two numbers is 48; the less number is 37: what is the greater ?
4. The difference of two numbers is 48; the greater number is 85 : what is the less ?
ART. 54. BY MULTIPLICATIOIT, Is found the amount of a number taken as many times as there are units in another, Art. 28.
Hence, having the cost of a single thing, to find the cost of any number of things, multiply the cost of one by the number of things.
1. If 1 yard of tape cost 3 cents, what will 5 yards cost?
ANALYSIS. — Five yards are 5 times 1 yard ; therefore 5 yards will cost 5 TIMES as much as I: the entire cost is found by multiplying the price of 1 yard by the NUMBER of yards.
The divisor and quotient being given, the dividend is found by multiplying together the divisor and quotient. Art. 37.
2. A divisor is 15; the quotient is 12: what is the dividend ?
3. An estate was divided among 7 children ; cach child received $325 : what sum was divided ? Ans. $3675.
ART. 55. BY DIVISIO IT, Is found how many times one number is contained in another. Art. 36. This enables us,
1. To divide any number into parts, each part containing a certain number of units.
2. To divide a number into any given number of equal parts.
Thus, if the cost of a number of things and the price of one are given, the number of things is found by division.
1. James spent 35 cents for oranges, and paid 5 cents cach : how many did he buy?
SOLUTION.—He got one orange for each time 5 cents are contained in 35 cents; 5 in 35, 7 times; therefore, he bought 7 oranges.
Knowing the cost of a given number of things, we obtain the price of one, by dividing the whole cost into as many equal parts as there are things.
2. If 4 oranges cost 20 cents, what does one cost? Solution. If 20 cents be divided into 4 equal parts, each part will be the cost of 1 orange. Placing 1 cent to each part, will require four cents. Hence, there will be as many cents in each part, as 4 cents are contained times in 20 cents; 4 in 20, 5 times; hence, in each part there will be 5 cents, the cost of one orange.
If the product of two factors be divided by either of them, the quotient will be the other. Art. 37.
Hence, if the dividend and quotient be given, find the divisor by dividing the dividend by the quotient.
Therefore, having the product of three numbers, and two of them given, the third can be found by dividing the product of the three numbers by the product of the two given numbers.
3. A dividend is 2875; the quotient, 125: find the divisor.
Ans. 23. 4. The product of three numbers is 3900: one number is 12, another 13: what is the third ?
ART. 56. PROMISCUOUS EXAMPLES. 1. In 4 bags are $500: in the first, 96; the 2d, 120; the 3d, 55 : what sum in the 4th bag ? Ans. $229.
2. Four mon paid $1265 for land; the first paid $243; the 2d, $61 more than the first; the 3d, $79 less than the 2d : how much did the 4th man pay? Ans. $493.
3. I have 5 apple-trees; the first bears 157 apples; 2d, 264; 3d, 305; 4th, 97; 5th, 123: I sell 428, and 186 are stolen : how many apples are left ? Ans. 332.
Review.–54. What is found by multiplication? Give an examplo.
55. What is found by division? What does it enable us to do? Give examples. If the dividend and quotient are given, how is the divisor found ? Having the product of three numbers; and two of them given, how is the other found ?