1. At what rate per cent., will $10 in 4 years amount to $12?

REMARK. From the amount subtract the principal, and the remainder will be the interest. Then proceed as in the preceding lesson.

2. At what rate per cent., will $12 in 3 years, amount to $13.44?

3. At what rate per cent., will $20 in 6 years, amount to $26 ?

4. At what rate per cent., will $24 in 10 years, amount to $36 ?

5. At what rate per cent., will $30 in 7 years, amount to $36.30 ?

6. At what rate per cent., will $50 in 10 years, amount to $75?

7. At what rate per cent., will $36 in 5 years, amount to $39.60 ?

8. At what rate per cent., will the interest for 20 years equal a given principal?

ANALYSIS.-With the interest at 100%, it would equal a given principal, or a given principal will double itself in 1 year, at 100 per cent.; and in 20 years, at

per cent., or 5 per cent.

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9. At what rate per cent., will a given principal double itself, in 4 years?

10. At what rate per cent., will a given principal double itself, in 3 years?

11. At what rate per cent., will the interest equal a given principal in 5 years?

12. At what rate per cent., will $80 in 7 years give $80 interest?

13. At what rate per cent., will $640 in 6 years give $640 interest?

14. At what rate per cent., will 25 cents in 8 years give 25 cents interest?

15. At what raie per cent., will $97 in 9 years give $97 interest?

16. At what rate per cent., will $372 in 25 years give $372 interest?

17. At what rate per cent., will $1 in 30 years give $1 interest?

18. At what rate per cent., will $15 in 12 years give $15 interest?

19. At what rate per cent., will $42 in 14 years give $42 interest?

20. At what rate per cent., will 5 cents in 163 years give 5 cents interest?

LESSON LXXI.

1. In what time will a given principal double itself, at 5 per cent.?

ANALYSIS.-A given principal will double itself in 100 years, at 1 per cent., and at 5 per cent., in of 100 years, which is 20 years.

2. In what time will a given principal double itself, at 4 per cent.?

3. In what time will $25, at 3 per cent., give $25 interest?

4 In what time will $275, at 6 per cent., give $275 interest?

5. In what time will the interest equal a given prin cipal, at 2 per cent.?

6. In what time will $4, at 7%, give $4 interest?

7. In what time will $94, at 9%, give $94 interest? 8. In what time will 5 cents, at 8 per cent., give 5 cents interest ?

9. In what time will $38, at 10 per cent., give $3g interest?

10. In what time will 1 dime, at 12 per cent., give 1 dime interest?

1. Bought a bushel of grass-seed for $5, and sold it for $7; what was the gain per cent.?

· ANALYSIS.—Since it was bought for $5, and sold for $7, the gain was $7-$5, which is $2. Therefore, of the cost equals the gain. Hence, the gain per cent. was 100 per cent., which is 40 per cent.

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2. A book was bought for $2, and sold for $3; what was the gain per cent.?

3. A shawl cost $5, and was sold for $8; what was the gain per cent.?

4. A cow was bought for $20, and sold for $25; what was the gain per cent.?

5. A merchant bought a hogshead of molasses for $80, and sold it for $95; what did he gain per cent.?

6. A barrel of pork cost $12, and was sold for $11; what was the loss per cent.?

7. A horse was bought for $140, and sold for $60; what was the loss per cent.?

8. Bought an orange for 4 cents, and sold it for 6 cents; what was the gain per cent.?

9. Bought a melon for 15 cents, and sold it for 20 cents; what was the gain per cent.?

10. Bought a book for 5 dimes, and sold it for 8 dimes; what was the gain per cent.?

11. Bought a hectometre of silk for $120, and sold it for $200; what was the gain per cent. ?

12. A bov sold melons, at the rate of 10 cents each

of which equaled his gain; how much would he have gained per cent., if he had sold them at 12 cents each?

13. A merchant sold sugar for $80 a hogshead, and thereby cleared of this money; if he had sold it at $92 a hogshead, what would he have gained per cent.?

14. A quantity of cloth was bought for $36, and sold for $43; what was the gain per cent.?

15. A horse was bought for $100, and sold for $95, what was the loss per cent.?

16. A man re-sold a kilogramme of wheat for $120, and cleared of its cost; how much money would he have lost per cent., if he had sold it for $80? 17. What per cent. of is? Of is? Of is? Of is ? Of is Of 2 is ? Of 31 is 27 ?

18.

of $6 is what per cent. of of $100?

19. of $28 is of what per cent. of § of $300? 20. Walter sold a horse for $120, and thereby gained of its cost; what would he have lost per cent. by selling it for $80 ?

1. A man bought a cow for $20; for what must he sell her, to gain 5 per cent.?

of

ANALYSIS.-If he gain 5 per cent., he gains, or the cost. of $20 is $1, the gain. Therefore, to gain 5 per cent., he must sell the cow for $20+$1, or $21.

2. A man bought a yoke of oxen for $100; how must he sell them, to gain 6 per cent.?

3. A man bought a barrel of flour for $10; for what must he sell it, to gain 10 per cent. ?

4. A gallon of wine was bought for 20 dimes; how must it be sold a pint, to gain 20 per cent.? 5. A hogshead of molasses cost $20; for what ought it to be sold a gallon, to gain 40 per cent.? 6. B. bought a horse for $80, and by selling it, lost 5 per cent.; for what did he sell it?

7. A wagon cost $140, and was sold at a loss of 5 per cent.; for what was it sold?

8. A merchant, by selling 40 metres of cloth for $164, lost 20 per cent.; what did it cost per metre?

9. If 3 decalitres and 5 litres of wine cost $140, how must it sell per litre to gain 20%?

10. B. lost 5 per cent. by selling a hectolitre of rum, which cost $80; for what did he sell it a litre ?

1. What principal will, in 4 years, at 5 per cent., amount to $60 ?

ANALYSIS.-If the interest of $1 for 1 year is 5 cents, for 4 years it is 4 times 5 cents, or 20 cents. Therefore,, or of the principal equals the interest; to which add, the principal, and we have of the principal equal to the amount, or $60. If of the principal is $60, of the principal is of $60, which is $10; and (the principal), is 5 times $10, which are $50.

2. What principal will, in 3 years, at 6 per cent., amount to $118?

3. What principal will, in 5 years, at 6 per cent., amount to $130 ?

4. What principal will, in 7 years, at 5 per cent., amount to $81?

5. What principal will, in 9 years, at 8 per cent., amount to $86?

6. What principal will, in 3 years, at 8 per cent., amount to $260 ?