161. WRITTEN EXERCISES.

17. After a loss of 10% in shrinkage a bin contained 375 bushels of potatoes, how many bushels 'were there at first?

18. A farmer sold 480 barrels of apples, which was 64% of all he had. How many barrels had he left?

19. If I save $720, or 80 %, of my income each year, what is my income?

20. A man drew from the bank $450, which was 15% per cent of all the money he had. How much money had he?

21. If I paid $5575 for a farm, and sold it at a loss of 15%, what did I get for it?

22. What number increased by 23% of itself is 7 995 ?

23. A man bought two horses. For the first he paid $156.25, which was 25% more than the cost of the second. What did the second horse cost?

24. What number lessened 25% of itself is 7 250 ? 25. On a bill of $347.50, only $319.70 was collected. What per cent was lost?

26. After paying 65% of my debts, I still owe $157.50. What were my debts at first?

27. In a school of 468 pupils, 12 on an average were absent every day. What was the per cent of attendance?

28. If I sell a span of horses for $468, and thus lose 22% per cent of the cost, what was the cost? 29. If a coal-dealer buys coal at $6 for the long ton, which is 2240 pounds, and sells at $6 for the short ton, which is 2000 pounds, what per cent does he make?

INTEREST.

162. Mr. Leonard borrowed of me $200, agreeing to pay me for its use for a year 6 % of the $200. How much did he owe me at the end of the year for the use of the $200 ?

How much did he owe in all?

Ans. $12.

Ans. $200 + $12, or $212.

163. Interest is money paid for the use of money. In the example above $12 is the interest paid for the use of $200 for a year.

164. The Principal is the sum for which interest is paid. In the example above $200 is the principal.

165. The Amount is the sum of the principal and interest. In the example above $ 212 is the amount.

166. The Rate is the per cent of the principal paid for its use for a year, or for any other specified time. In the example above 6 % is the rate.

NOTE 1. When no time is specified, a year is meant; and when no rate is named, 6 % is understood.

NOTE 2. In computing interest it is the custom to reckon 30 days a month, and 12 months a year.

167. ORAL EXERCISES.

1. What is the interest of $8 at 5% for 1 year? for 2 years and 3 months?

Solution.

At 5% the interest of $1 for 1 year is 5 cents; the interest of $8 is 8 times 5 cents 40 cents, 1st Ans. For 1 year at 5% the interest of 8 is 40 cents; therefore for 2 years and 3 months, or 24 years, it is 24 times 40 cents= 90 cents, 2d Ans.

2. What is the interest of $40 for 1 year at 5%? at 6%? at 8% ? at 10% ?

3. What is the interest of $5 for 1 year at 6% ? for 2 years? for 4 years?

4. What is the interest of $25 for 1 year at 4% ? at 5%? at 10% ?

5. What is the interest of $100 at 6% for 1 year? for 6 months? for 3 months? for 2 months?

6. What is the interest of $1 at 6% for 1 year? for 1 month? for 2 months? 3 months? 6 months? 9 months?

7. What is the interest of $1 at 6% for 6 days? for 1 day? for 12 days? for 18 days?

Solution.

As the interest of $1 for 1 year, or 12 months, is 6 cents, for 1 month the interest is of 6 cents, that is, is 5 mills; and the interest for 6 days is, or of 5 mills, that is, is 1 mill; and therefore for one day the interest of $1 is of a mill; for 12 days, 2 mills; and for 18 days, 3 mills.

8. What is the interest of $1 for 1 year at 6% ? at 8%? at 9% ?

9. What is the interest of $5 for 2 years 6 months at 8% ?

168. WRITTEN EXERCISES.

10. What is the interest of $345 for 2 years 8 months at 6 % ?

11. What is the amount of $66.75 for 3 years 6 months at 8% ?

12. What is the interest of $53.75 for 2 years at 6% ?

13. What is the interest of $85.15 for 1 year 4 months at 6% ? Ans. $6.812. 14. What is the interest of $525 for 2 yr. 9 m. at 8% ?

15. What is the interest of $632.25 for 3 yr. at 10 % ?

6 m.

16. What is the amount of $127.42 for 2 yr. 2 m. at 9% ?

169. The method of computing interest given above is applicable to any example in interest. But the method given below is the one generally used by business men, and in most cases is much more expeditious.

To find the interest on any sum of money, at 6 %, for any given time.

170. At 6 %, any sum of money in 2 months, or of a year, will gain 1 %, or 0.01 of itself; and in 10 of 2 months, that is, of 60 days, or 6 days, it will gain of 1%, or 0.001 of itself.

17. What is the interest of $382 for 3 months

For two months we take of the principal, or $3.82; for 1 month of $3.82; and for 6 days 1000 of the principal, or $0.382. The sum of these, or $6.112, is the interest of $382 for 3 months and 6 days.

18. What is the interest of $218 for 1 month 3 days?

19. What is the interest of $846 for 9 months