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4. If 10 men can build a wall in 40 days, how many men will be required to build the same wall in 10 days ?

Given 10 men and 40 days.
Required ? and 10 days.

40 x 18 = 40 men.

An increase in the required term of the ratio demands a diminution in the unknown.

5. If 12 horses eat a certain quantity of hay in 54 weeks, how many horses will consume the same hay in 9 weeks ?

Ans. 72 horses. 6. If a man perform a journey in 24 days when the days are 9 hours long, how many days will it take him when the days are 12 hours long? Ans. 18 days.

7. If 10 men reap 30 acres of wheat in 3 days, how long will it take 5 men to reap the same field ? Ans. 6 days.

COMPOUND RATIO.

When there are two or more ratios, it is termed Compound Ratio; thus,

If 3 men in 12 days build 40 rods of wall, how many
rods will 9 men build in 24 days ?
Given

3 men, 12 days, 40 rods.
9 men, 24 days, ?

&

6

40 x x = 240 rods.

REM.--Each ratio is direct.

If 12 men dig a ditch 20 rods long in 18 days by work

ing 8 hours a day, how many men will dig a ditch 40 rods long in 24 days, working 6 hours a day? Given 12 men, 20 rods, 18 days, 8 hours.

? 40 rods, 24 days, 6 hours.

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EXEMPLIFICATION.—The longer the trench, the more men it will take, and the ratio is direct; but the greater the number of days and the more hours of each day, the fewer men would be required; hence these two ratios are inverse.

COR.—Each ratio must be dealt with as in the preceding article.

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1. If 4 men in 12 days build 40 rods of wall, how many rods will 6 men build in 18 days ?

Given 4 men, 12 days, 40 rods.
Required 6 men, 18 days, ?

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2. If 18 men dig a trench 30 rods long in 24 days by working 8 hours a day, how many men will dig a trench 50 rods long in 64 days working 6 hours a day?

Given 18 men, 30 rods, 24 days, 8 hours.
Required ? 60 rods, 64 days, 6 hours.

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Observe, the longer the trench, the more men will be

required; but the more days the less men, and the more bours the less men ; the first ratio is direct, the other two inverse.

* 3. If 6 men in 16 days of 9 hours each, build a wall 20 feet long 6 feet high and 4 feet thick, in how many days of 8 hours each will 24 men build a wall 200 ft. long 8 ft. high and 6 ft. thick?

Ans. 90 days. 4. If 12 men mow 24 acres of grass in 2 days of 10 hours each, how many hours a day must 16 men work to mow 80 acres in 4 days ? Given

24 acres, 2 days, 10 hours. Required 16 men, 80 acres, 4 days, ?

12 men,

5

10 x H x x = e = 124 hours.

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5. If $100 in 12 months gain $6, how long will it take $600 to gain $24 ?

Given $100 prin., 12 mo., $6 interest.
Required $600 prin., ? $24 interest.

2

12 xx4

= 8 months. 6. If 8 horses eat 42 bushels of oats in 24 days, how many bushels will suffice 16 horses 36 days?

Ans. 126 bushels. 17. If it cost $30 to transport 6 cwt. 2 qrs. 180 miles, what will be the cost of transportation of 19 cwt. 2 qrs. 270 miles ?

Ans. $135. 8. If 42 men in 270 days of 83 hours each can build a wall 983 yards long 71 ft. high and 24 ft. thick, in how many days of 113 hours each can 63 men build a wall 45} yds. long 61 ft. high and 31 ft. thick ? 270 x 43 x 12 x X136 x 19 x 35 x 347 X1 X= 68 da.

REM.-When all the terms are arranged in ratios, the cancella. tion is more easily performed. It is better, however, first to arrange the like terms together, and then mark the direct and indirect ratios.

9. If 14 men can reap 84 acres in 6 days, how many men must be employed to reap 44 acres in 4 days?

10. A wall 600 feet in length is to be built in 30 days; 10 men have been employed at it for 12 days, and have built 240 feet. How many more men must be employed in order to finish it in the given time?

Ans. The 10 men will finish it in the given time. 11. If 12 men make 600 pairs of shoes in 30 days, how many men will make 12000 pairs in 90 days?

Ans. 80 men.

SIMPLE EQUATIONS.

An Equation consists of two equal members placed opposite each other with the sign of equality between them. The members are called the right and left hand members. Thus, 8 + 4 = 6 + 6.

The analysis of simple ratios may be rendered by equations, thus:

1. If 12 bushels of wheat cost $15, what will 42 bushels cost?

12 bu. = $15. Divide both members by 12. 1 bu. = $1.25. Multiply both members by 42. 42 bu. = $52.50.

That is, if 12 bushels equals or costs $15, one bushel will cost of $15; that is, $1.25 and 42 bushels will cost $1.25 x 42 = $52.50.

Ax. 1. If equals be multiplied by equals, the products will be equal.

Ax. 2. If equals be divided by equals, the quotients will be equal.

2. If 15 bushels of oats cost $4.50, what will 75 bushels cost?

15 bu. = $4.50. Divide both members by 15.

1 bu. =

.30. Multiply both members by 75. 75 bu. = $22.50.

3. If 20 bushels of wheat yield 4 barrels of flour, how many bushels will yield 15 barrels of flour ?

4 barrels = 20 bushels.
1 barrel = 5 bushels.

15 barrels = 75 bushels. 4. A man bequeathed his estate of $10000 to his son and daughter; the son to have $2000 more than the daughter. What was the share of each ?

The work may be shortened by letting x represent one of the unknowns; thus, Let

= daughter's share.

X + 2000 = son's share. Add the 2 shares, 2x + 2000 = 10000

8000

4000 daughter's share.

XC + 2000 I 6000 son's share. COR. 1. If equals be subtracted from equals, the remainders will be equal.

2. If equals be divided by equals, the quotients will be equal..

5. A and B hired a pasture for $55; A paid 13 dollars more than B. What did each pay?

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