17. These children are standing by a cord of wood. It is 8 ft. long and the wood is cut in 4-foot lengths. How high is the pile? 18. How many cubic feet are there in 33 cords? 19. A pile of 4-foot wood is 4 rd. long and 6 ft. high. How many cords does it contain? 20. A pile of 4-foot wood is 75 ft. long and 7 ft. high. How many cords does it contain ? 21. How much is a pile of 4-foot wood 60 ft. long and 6 ft. high worth at $3.75 a cord? 22. How much is a pile of 4-foot wood 75 ft. long and 7 ft. high worth at $4 a cord? 23. A pile of wood 8 ft. long and 4 ft. high is usually called a cord, the price varying with the length of the wood. How many cords in a pile 28 ft. long and 6 ft. high? 24. A pile of wood is 50 ft. long and 5 ft. high. How many cords does it contain? 25. How much is a pile of wood 30 ft. long and 5 ft. high worth at $3.50 a cord? 139. Addition of Compound Numbers. The general principles for adding compound numbers are the same as those for adding integers. The only difference arises from the fact that in integers ten units of each order always make one unit of the next higher, while in compound numbers the number of units of a lower denomination required to make one unit of the next higher varies with the denomination we are using. Required to add 2 hr. 38 min. 42 sec., 3 hr. 25 min. 36 sec., and 5 hr. 17 min. 58 sec. sec. The sum of the seconds is 136 sec., or 2 min. 16 sec. We write the 16 sec. under the seconds, and add the 2 min. to the minutes. The sum of the minutes is 82 min., or 1 hr. 22 min. Writing the 22 min., we add the 1 hr. to the hours. The sum of the hours is 11 hr. Hence the result is 11 hr. 22 min. 16 sec. hr. min. 11 22 16 In practical life to-day we rarely have to add numbers of more than two denominations, and hence the examples given in this book are in general of not more than two denominations. 6. If a boy weighs 73 lb. 12 oz. and his sister weighs 69 lb. 12 oz., how much do they weigh together? 7. The class in cooking had one piece of meat weighing 1 lb. 14 oz. and another weighing 2 lb. 9 oz. What was the total weight? 44. Add 16° 27' 32", 37° 48′ 16′′, 48° 29' 36", 28° 13′ 23′′. 45. Add 2 A. 40 sq. rd., 3 A. 80 sq. rd., 4 A. 30 sq. rd., 10 sq. rd. 46. Add 5 sq. rd. 6 sq. yd., 7 sq. rd. 201 sq. yd., 6 sq. rd. 4 sq. yd. 47. Add 9 cu. yd. 18 cu. ft., 7 cu. yd. 12 cu. ft., 24 cu. ft. 920 cu. in., 808 cu. in. 48. Add 21 lb., 4 lb. 4 oz., 33 lb., 5 lb. 8 oz., 6 lb. 9 oz., 51 lb., 2 lb., 8 oz. 140. Subtraction of Compound Numbers. The general principles for subtracting compound numbers are the same as those for subtracting integers, except as explained in addition. hr. min. sec. 22 16 27 14 25 40 7 50 47 For example, from 22 hr. 16 min. 27 sec. required to subtract 14 hr. 25 min. 40 sec. - 40 sec. Since we cannot subtract 40 sec. from 27 sec., we take 1 min. (60 sec.) of the 16 min. Then 60 sec. + 27 sec. = 87 sec., and 87 sec. 47 sec. Since we cannot subtract 25 min. from 15 min., we take 1 hr. (60 min.) of the 22 hr. Then 60 min. + 15 min. = 75 min., and 75 min. - 25 min. = 50 min. Then 21 hr. - 14 hr. = 7 hr. The difference is 7 hr. 50 min. 47 sec. EXERCISE 78 1. The class made a lamp screen. Each wing was 1 ft. 6 in. high and 93 in. wide. It was how much higher than wide? 2. A girl tried some bluings in laundry work, using 2 gal. 1 qt. in one experiment and 2 qt. in another. How much more did she use in the first experiment than in the second? 3. If one boy is 5 ft. 1 in. in height and another is 4 ft. 10 in. in height, how much taller is the first boy? 8. A lady buys 7 yd. of cloth and uses 27 in. How much has she left? 9. A field is 42 rd. 8 ft. long and 24 rd. 12 ft. wide. The length of the field is how much more than the width? 10. A man starts out to travel 3 200 rd. how much farther has he to mi. After he has gone go ? |