SPECIAL CASES IN MULTIPLICATION 333. Oral Questions. 1. Ten times 20 horses are how many horses? 2. To multiply 20 by 10, what figure is written after 20? 3. Ten times 70 houses are how many houses? dollars? 4. A hundred times 3 dollars are how many 5. To multiply 3 by 100, what figures are written after 3? 334. Written Problems. 1. What is the product of 10 and 125? 2. 3. Find the cost of 30 acres of land at $19 an acre. 4. In 1 mile there are 5 280 feet; how many feet are there in 40 miles? 5. If there are 29 telegraph poles to the mile, how many telegraph poles in 50 miles? 6. Seventy mules, at $125 each, would cost how much? 7. The multiplicand is 79; the multiplier is 80; what is the product? 8. The multiplier is 90; the multiplicand is 89; what is the product? 9. The multiplier is 100; what is the product? 76 100 7 600 10. How much would 200 horses, at $75 per head, cost? II. A farmer averaged 22 bushel of oats per acre on 300 acres; how many bushels in all? 12. Find the sum of the products of 9×337, 6×479, 7x698. 13. Find the sum of the products of 8×376, 7×987, 6×679. II. Multiply by the 6 tens, placing the first figure under the teus of the first product, and so on. 365 4465 III. Multiply by the 3 hundreds, placing the first figure under the hundreds of the other products, and so on. 5358 2679 IV. Add the three partial products. 325945 14. The multiplicand is 6 812; the multiplier is 203; what is the product? Since there is no ten in the multiplier, there are only two partial products. 15. A cotton merchant bought 104 bales of cotton averaging 469 pounds. What was the entire weight? 6 812 203 336. Oral Questions. 1. One yard equals 3 feet; how many feet in 21 yards. Is it 21 times 3, or 3 times 21? 337. The small number may be used as the multiplier; the answer will be like the true multiplicand. 2. Seven days make a week. How many days are in 52 weeks? Is it 7 times 52, or 52 times 7? 3. 52×7 = ? 7×52=? 338. Written Problems. 1. A farmer bought 1728 acres of land at $15 per acre; what was the whole cost? EXPLANATION. When the multiplier is a much larger number than the multiplicand, the numerical product is more quickly found by reversing the factors. The product, however, is of the same nature as the true multiplicand. In solving the problems below, write the word multiplicand opposite each true multiplicand. 2. What would be the cost of 447 sheep at $7 a head and 180 cattle at $20 a head? 3. A farmer made an average profit of $4 per acre on 76 acres in cotton, and $5 per acre on 69 acres in oats; what were his profits on the two crops? 4. A man bought 125 acres of land at $6 per acre, and 10 acres at $27 per acre; what was the whole cost? 5. How much was paid for a farm of 239 acres at $36 an acre? 6. A farmer gathered 42 bushels of corn per acre from 279 acres; find the total yield. 7. To fence a pasture the owner finds that 3 598 panels, each of 12 rails, will be required; how many rails will it take for the pasture? 8. The multiplier is 455; the multiplicand is $500; find the product. What was the cost of 1 357 head of cattle sold at $22 a head? 10. The total yield of sweet potatoes in one county was 15 798 bushels; how many pounds at 55 pounds to the bushel? II. If there are 30 telegraph poles to the mile, how many are on a line 279 miles long? 340. Oral Exercises. 1. In how many hours will a train run 400 miles at 40 miles an hour? 2. At 25 miles an hour, how far will a train run in 4 hours? 3. What number is one fourth of 100? 4. Four boys catch 100 fish; if they share equally, how many will each have? 5. How many are 25+25+25+25 ? How many are: 1. A gentleman sold a plantation for $23 750, which was $4 960 more than he paid for it; what did it cost him? 2. The minuend is 671 420; the subtrahend is 483 739; what is the remainder? 3. Find cost of steerage passage on a steamer from New Orleans to New York for a family of 9 at $19 each. 4. A farmer carried to mill 9 bushels of wheat, weighing 60 pounds to the bushel, and 8 bushels of corn, weighing 56 pounds to the bushel. How many pounds of grain did he carry to mill? 5. In 1 mile there are 1 760 yards; how many yards are in 24 miles? |