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31. When the mercury in the tube of a barometer is 30 in. high, the pressure of the atmosphere is about 15 lbs.

for every square inch. What will be its pressure when the mercury stands 25 in. high?

32. A cistern containing 60 hhds. of water has two pipes open, by one of which 3 gals. of water per minute run in, and by the other 9 gals. run out. In how many hours will the cistern be emptied?

33. How many pounds of cement will be required to plaster an open cistern whose dimensions are 4 ft. long, 3 ft. wide, and 23 ft. deep, if the cement on a square foot weighs 6 lbs.?

34. How many tons of water will the cistern in example 33 hold, if a cubic foot of water weighs 1000 oz.?

35. What will be the cost of covering with paper yd. wide the four walls of a room 21 ft. long, 16 ft. wide, and 10 ft. high, if the cost of the paper is 12 cts. per yard, and no allowance is made for doors and windows?

36. What is the breadth of a rectangular field containing 7 A., if the length is 242 yds.?

37. A certain watch gains 3 sec. in 24 hrs., and another loses 2 sec. in the same time. If both be set right on Monday at noon, what will be the difference between them at 6 o'clock (true time) the next Saturday evening?

38. A milkman paid a farmer $3.20 for ten 2-gal. cans of milk. He lost 20 qts. At what price per quart must he retail the remainder to gain 8 cts. a gallon? 39. A man who had of a square mile of woodland sold 12 sq. rds. How much had he left?

40. How many yards of Florence silk yd. wide will be required to line 19 yds. of camel's hair cloth 14 yds. wide?

41. How many days from Sept. 16, 1882, to Feb. 12, 1884 ? 42. A miller makes 154 bbls. of flour from 885 bu. of How many bushels on the average are

wheat.

required for a barrel of flour?

43. What must be the length of a walk 24 ft. wide to contain 38 sq. ft.?

44. A cistern 7 ft. long and 5 ft. wide contains 105 cu. ft. What is its depth? how many gallons of water will

it hold?

45. What must be paid for a pile of wood 25 ft. long, 3 ft. high, and 4 ft. wide at $5.50 per cord?

46. Each person on the average breathes 28 cu. ft. of air in an hour. How many hours will the air in a room 14 ft. long, 12 ft. wide, and 6 ft. high last 12 men?

47. Sound travels at the rate of 1130 feet a second.

How

long after the flash will the clap of thunder come
when the cloud is 2 mi. 1000 yds. distant?

48. There are 9 oz. of iron in the blood of 1 man. How
many men would furnish iron enough in their veins
to make a ploughshare weighing 221⁄2 lbs.?

49. The fore wheel of a carriage is 4 ft. 7 in. in circumference, and the hind wheel 5 ft. 6 in. How many more times will the fore wheel turn than the hind wheel in going a distance of 1 mi.?

50. A boarding-house uses 3 pks. of potatoes daily. At 87 cts. per bushel, what will be the expense for potatoes during October, November, and December?

r

CHAPTER X.

PERCENTAGE.

197. 1. A boy gave away 6 marbles out of every hundred he had. How many did he give away out of 400?

of 600? of 1000?

2. A man had 300 sheep, and sold 10 out of every hundred. How many did he sell?

3. A man sold 7 tons of coal out of every hundred he had. How many did he sell out of 900 tons?

4. A man sells 11 lbs. of sugar out of every hundred he has. How many pounds will he sell out of 500? How many pounds will he have left?.

198. In considering the increase or decrease of quantities, we usually employ the number 100 as the representative of the quantity considered.

199. Instead of using the phrases 6 in every hundred, 10 in every hundred, 7 in every hundred, 11 in every hundred, we say 6 per cent, 10 per cent, 7 per cent, 11 per cent. The words per cent therefore mean in every hundred.

200. The symbol % is used for the words per cent.

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10%?

What common fraction of a number (in its lowest terms) is:

25%? 81%?

121%? 125% ?

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201. Express % as hundredths and as a common frac⚫

tion.

=

1% = 0.001200.

In like manner express as hundredths and also as com

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202. Find 8% of 250 bu. of corn.

8% of a number is 8 hundredths of the number. 0.08 of 250 bu.

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2. 5% of 1000 bricks.

3. 8% of 200 ft. of board. 4. 6% of 90 dys.

5. 10% of 150 cds. of wood. 6. 20% of 250 prs. of gloves. 7. 25% of 120 horses.

8. 80% of 400 A.

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13.

75% of 40 hens.

14. 60% of 20 girls.

15. 16% of 60 lbs. of butter.
16. 371% of 120 gals. of syrup.

17. 621% of 800 soldiers.

18. % of 500 bu. of wheat.

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9. A farmer having a flock of 1200 sheep lost 37% of them. What per cent of them, and how many sheep, had he left?

10. If copper ore yields 6% of pure metal, how many pounds of copper will be obtained from 1 t. of ore?

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