a b triangles are alike in every respect? 5. Draw two triangles, the angles of one being equal to the but whose angles are unequal? Geometry. 208. CONSTRUCTION PROBLEMS-TRIANGLES. 1. Draw a triangle whose base, ab, is 3 inches long. Make the angle a, 55° and the angle 6, 35o. The apgle c should be degrees. Measure the three sides. Observe that the longest side is opposite the greatest angle and the shortest side opposite the smallest angle. 2. Draw a triangle two of whose sides are equal. Measure and compare the angles opposite the equal sides. Observe that a triangle, two of whose sides are equal, has two angles equal; and conversely if two angles of a triangle are equal, two of the equal. 3. If two triangles have the three sides of one equal to the three sides of the other, each to each, do you think the two 4. If two triangles have the three angles of one equal to the three angles of the other, each to each, do you think the are necessarily alike in every respect? angles of the other, and the sides of one not being equal to 6. Is it possible to draw a triangle whose sides are equal, sides are two triangles the sides of the other. * 209. MISCELLANEOUS REVIEW. 1. Without a pencil, change each of the following frac 3 1 5 7 3 7 5 7 9 tions to hundredths: 5 8 8 10' 25' 50' 12' 33' 163 60 30 45 60 60 60 60 -.t 500'200' 900' 150 250' 125' 663 2. Butter that cost 25¢ a pound was sold for 29¢ a pound. The gain was equal to what part of the cost ?. The gain was equal to how many hundredths of the cost ? 3. The taxes on an acre of land which was valued at $600, were $12. The taxes were equal to what part of the valuation? The taxes were equal to how many hundredths of the valuation ? 4. Mr. Jones purchased 500 barrels of apples. He lost by decay a quantity equal to 75 barrels. What part of his apples did he lose? How many hundredths of his apples did he lose ? 5. Regarding a month as 30 days and a year as 360 days, what part of a year is 7 months and 10 days ? How many hundredths of a year in 7 months and 10 days ? How many thousandths of a year ? How many ten-thousandths of a year? 6. One cord 48 cubic feet is what part of 4 cords 16 cubic feet? Change the fraction to hundredths; to thousandths; to ten-thousandths. 7. One mile 240 rods is what part of 3 miles 160 rods? Change the fraction to hundredths; to thousandths; to tenthousandths. 8. From a bill of $175 there was a discount of $14. The discount is equal to low many hundredths of the amount of the bill ? * Since 100 is of 150, take 3 of 60. † 100 is 11 times 663. PERCENTAGE. 210. Per cent means hundredth or hundredths. Per cent may be expressed as a common fraction whose denominator is 100, or it may be expressed decimally ; thus, 6 per cent 281 1 1 or .06; 284 per cent = or .284; } per cent 100 100 or .005. Note.—Instead of the words per cent sometimes the sigu (%) is used ; thus 6 per cent may be written 6 %. 211. The base in percentage is the number of which hundredths are taken ; thus, in the problem, Find 11% of 600, the base is 600; in the problem, 16 is what per cent of 800 ? the base is 800; in the problem, 18 is 3 % of what? the base is not given, but is to be found by the student. Observe that whenever the base is given in problems like the above, it follows the word of. 212. There are three cases in percentage and only three. Case I. To find some per cent (hundredths) of a number, as : find 15% of 600. Case II. To find a number when some per cent of it is given, as : 24 is 8 % of what number? Case III. To find what per cent one number is of another, as : 12 is what % of 400 ? Observe that a thorough knowledge of fractions is the necessary preparation for percentage. The work in percentage is work in fractions, the denominator employed being 100. Percentage. 213. CASE I. Find 17 per cent (.17) of 8460. NOTE 1.—No new rule is necessary for performing this operation. We may find of a number by finding 3 times 1 fourth of it; that is, by multiplying it by. So we may find .17 of a number by finding 17 times 1 hundredth of the number; that is, by multiplying by .17. Operation. Explanation. V 84 60 .17 592.20 846.0 1438.20 One per cent (1 hundredth) of 8460 is 84.60 ; 17 per cent (hundredths) of 8460 is 17 times 84.60, or 1438.20. PROBLEMS. 9. Find 65% of 6120; of 5252; of 31.40. (a) Find the sum of the twenty-seven results. 10. A sold goods for B. As remuneration for his services he received a sum equal to 12% of the sales. He sold $2146 worth of goods. How much did he receive for his services ? 11. C is a collector of money. For this service he charges a commission of 6%; that is, his pay is 6% of the amount collected. He collected for D $375. How much should he' pay over to D, and how much should he retain as pay for collecting ? Percentage. 214. CASE II. 673.20 is 17 per cent (.17) of what number? Operation No. 1. Explanation. 17) 673.20(39.60 51 100 Since 673.20 is 17 hundredths of the 163 3960. number, 1 hundredth of the number 153 is 1 seventeenth of 673.20, or 39.60; and 100 hundredths 100 times 39.60, 102 or 3960. Explanation. We may find 100 seventeenths of a number by finding 1 seventeenth of a 163 hundred times the number. 100 times 153 673.20 is 67320. 1 seventeenth of 102 67320 is 3960. 102 Observe that in the second operation we simply divide the number by 17 hundredths. Dividing by .17 is finding 109 of the dividend, just as dividing by is finding of the dividend, and dividing by 1 is finding { of the dividend. Sometimes the process may be shortened by writing the per cent as a common fraction and reducing it to its lowest terms; then using the reduced fraction instead of the one whose denominator NOTE. is 100. PROBLEMS. 7. 360 is 2% of what number? |