LESSON XII. 1. In what time will a given principal double itself, at 5 per cent? SOLUTION.-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 a given principal double itself, at 3 per cent? 4. In what time will a given principal double itself, at 6 per cent? 5. In what time will a given principal double itself, at 2 per cent? 6. In what time will a given principal double itself, at 7 per cent ? 7. In what time will a given principal double itself, at 9 per cent? 8. In what time will a given principal double itself, at 8 per cent? 9. In what time will a given principal double itself, at 10 per cent? 10. In what time will a given principal double itself, at 12 per cent ? LESSON XIII. 1. Bought a bushel of grass-seed, for $5 and sold it for $7; what was the gain per cent? If on $5 SOLUTION. Since it was bought for $5 and sold for $7, the gain must have been $7-$5, which is $2. the gain is $2, on $1 it will be 3 of a dollar, (or on 1 cent). of a cent If the gain on 1 cent is of a cent, on 100 cents, it is 100 times of a cent, which are 200 or 40 per cent. 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? 3. 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 quantity of silk for $120, and sold it for $200; what was the gain per cent? 12. A boy sold melons, at the rate of 10 cents apiece, of which equaled his gain; how much would he have gained per cent, if he had sold them, at 12 cents apiece? 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? LESSON XIV. 1. A man bought a cow for $20; for what must he sell her, to gain 5 per cent on the cost? SOLUTION.-If he gains 5 cents on 100 cents, on 1 cent he will gain of 5 cents, which is, or of a cent. Consequently he must sell it for 2 of what it costs, &c. 2. A man bought a yoke of oxen for $100; how must, he sell them, to gain 6 per cent on the cost? 3. A man bought a barrel of rum for $10; for what must he sell it, to gain 10 per cent on the cost? 4. A gallon of wine was bought for 20 dimes; how must it be sold a pint, to gain 20 per cent on the cost? 5. A hogshead of molasses cost $20; for what ought it to be sold a gallon, to gain 40 per cent on the cost? 6. B bought a horse for $80, and by selling it, lost 5 per cent on the cost; for what did he sell it? 7. A wagon cost $140 dollars, and was sold for 5 per cent less than it cost; for what was it sold? 8. A merchant, by selling 40 yards of cloth for $164, lost 2 per cent on the cost. What did it cost per yard? 9. If a quart of brandy cost 50 cents, how must it be sold a gill, to lose 4 per cent? 10. B lost 5 per cent, by selling a gallon of rum, which cost 80 cents; for what did he sell it a gallon? LESSON XV. 1. What principal will, in 4 years, at 5 per cent, amount to $60 ? SOLUTION. We find (by Lesson IV,) that of the principal equals the interest. (the principal) and (the interest) added, is g of the principal, which equals the amount. If g of the principal is $60, 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 33 amount to $260 ? 7. What principal will, in 43 amount to $640? 8. What principal will, in 5 amount to $42 ? 9. What principal will, in 62 amount to $87 ? years, at 8 per cent, years, at 6 per cent, years, at 7 per cent, years, at 7 per cent, 10. What principal will, in 83 years, at 6 per cent, amount to $76 ? REMARK.-The present worth of a debt, payable at some future time, without interest, is such a sum, as will, in the given time, and at the given rate per cent, amount to the debt. Hence the present worth of any sum of money, payable at some future time without interest, may be found in the same way that we found the principal, when we had given the amount, time, and rate per cent. See the above solution. 11. What is the present worth of $26, due 5 years hence, at 6 per cent? Ans. $20. 12. What is the present worth of $14, due 8 years hence, at 5 per cent? 13. What is the present worth of $110, due 5 years hence, at 5 per cent? 14. What is the present worth of $86, hence, at 9 per cent ? due 8 years 15. What is the present worth of $102, due 9 years 16. What is the present worth of $72, due 4 years 17. What is the discount on $46, due 3 at 5 per cent? years hence, REMARK.-The discount equals the amount minus the present worth. 18. What is the discount of $54, due 5 years hence, 19. What is the discount of $65, due 5 years hence, 20. What is the discount of $93, due 3 years hence, 21. What is the present worth of $186, due 4 22. What is the present worth of $66, due 51 23. What is the present worth of $128, due 4 1. If I sell cloth, at $2.50 a yard, and thereby gain SOLUTION.-25 per cent is of the cost (Lesson II.) † 2. A horse was sold for $38, which was at a loss 3. If I sell cloth, at $2.50 a yard, and thereby gain 4. If I sell cloth, at $4.40 a yard, and thereby gain |