46. WRITTEN EXERCISES. 21. In one year there are 365 days. How many days are there in 3 years? By addition. 365 66 By multiplication. Sum, 1095 days. = Product, 1095 days. the number of days in 3 years can be obtained by adding, as shown at the left; or, more briefly, by multiplying; thus, 3 times 5 units: 15 units=1 ten and 5 units; writing the 5 units in the units' place, we then say 3 times the 6 tens are 18 tens, and add the 1 ten previously obtained, making 19 tens 1 hundred and 9 tens; writing the 9 tens in the tens' place, we then say 3 times 3 hundreds are 9 hundreds, and add the 1 hundred previously obtained, making 10 hundreds 1 thousand and 0 hundreds; and these written in their place give the true product, 1095 days. 22. A certain house has 43 windows. How many windows would 5 such houses have? 23. If Henry picks 127 apples in an hour, how many can he pick in 9 hours? 24. If a steamer can go 258 miles in a day, how far can it go in 3 days? 25. In a certain town there are 415 voters. How many would there be in 9 such towns? 26. If a bushel of corn is worth 75 cents, what are 8 bushels worth? 27. If a man can earn $658 a year, how much can he earn in 7 years? s? 47. ORAL EXERCISES. 52. At 6 cents a pound, what will 11 pounds of sugar cost? 53. If a wheel revolves 8 times in a minute, how many times will it revolve in 9 minutes? 54. If I pay 10 dollars for 1 stove, how much must I pay for 7 stoves? 55. In an orchard there are 8 trees in a row. How many trees are there in 6 rows? 56. If a boy earns 9 dollars a month, how much will he earn in 6 months? 57. How many dollars will pay for 12 barrels of flour at 6 dollars a barrel? 58. If a pair of skates cost 3 dollars, how much will 12 pairs cost? 59. At 11 cents a pound, what will 8 pounds of walnuts cost? 60. If a ship sails 9 miles an hour, how far will it sail in 7 hours? 61. At 4 cents a sheet, what will 8 sheets of gingerbread cost? 62. If 2 men can build a wall in 4 days, how long will it take 1 man to build it? 63. If 6 men can do a piece of work in 8 days, how long will it take 1 man to do it? 64. If 5 men can reap a field of grain in 6 days, how long will it take 1 man to reap it? 65. How many are 9 times 8? 5 times 3? 12 times 5? 11 times 6? 4 times 10? 9 times 7? 8 times 4? 6 times 5? 10 times 6? 4 times 10? 66. How many are 8 x 8? 9 x 1? 12 × 6? 7 x 7? 10 x 8? 6 x 6? 10 x 2? 7 x 3? 9 x 5? 4 x 4? 4 x 9? 8 x 3? 7 × 4? 67. How many are 5 × 4? 6 × 9? 8 × 5? 9 × 3? 7 x 4? 9 x 10? 10 × 5? 11 × 5? 12 × 5? 68. How many are 3 × 10? 3 x 11? 3 × 12? 4 x 10? 4 x 11? 4 x 12? 9 × 9? 69. How many are 12 × 2? 12 × 4? 12 × 7? 12 × 8? 12 × 9? 12 × 10? 12 x 11? 12 × 12? 48. WRITTEN EXERCISES. 70. Multiply 364 by 23. Multiplicand, 364 23 1092 728 First multiply by the 3 as though it was the only figure in the multiplier; then multiply by the 2, and write the right-hand figure of this product in the place of tens; for multiplying by the 2 tens is the same as multiplying by 20, and 20 times 4 units are 80 units 8 tens; that is, the product of units by tens is tens. Multiplying each figure of the multiplicand by the 2 tens, and adding the 1092 and the 728 tens, we obtain the true product, 8372. Product, = 71. If 45 men can build a wall in 37 days, how long will it take 1 man to build the same wall? 72. What is the value of 27 horses at $87 each? 73. If a train of cars runs 24 miles an hour, how far will it run in 36 hours? 74. How many meters of cloth in 783 pieces, if each piece contains 39 meters? 75. Multiply 43.75 by 35. 43.75 35 218 75 13125 Ans. 1531.25 49. An example in multiplication may be proved by multiplying the multiplier by the multiplicand, and if the work is correct the numerical product will be the same as before. 50. As removing a figure one place to the left multiplies it by ten, two places by a hundred, etc., therefore to multiply by 10, 100, 1000, or 1 with any number of ciphers annexed, Rule. Move the decimal point as many places to the right as there are ciphers in the multiplier. |