423.-1. When the allowance for the use of money is 6%, how many cents is it for $1, or 100 cents? How much is it for $100?

2. When the allowance for the use of $1 is 6 cents, what is the rate per cent.? When it is 5 cents? 3. When the allowance for the use of $100 for 1 year is $6, what is the yearly rate per cent.? When it is $5, what is the yearly rate per cent.?

4. When the yearly allowance for the use of money is at the rate of 6%, what is the allowance for the use of $5 for 3 years?

SOLUTION.-The allowance for 1 year at 6% is 18 of the base; hence, the allowance for the use of $5 for 1 year must be roo of $5, or $.30, and for the use of $5 for 3 years must be 3 times $.30, or $.90.

5. What is the allowance for the use of $8 for 4 years, at a yearly rate of 7% ?·

6. What is the allowance for the use of $25 for 5 years, at a yearly rate of 4% ?

7. What is the allowance for the use of $50 for 4 months, at a yearly rate of 6% ?

SOLUTION.-The allowance for the use of $50 for 1 year at 6 per cent. is $3; hence, for 4 months, or of a year, it must be of $3, or $1.

8. What is the allowance for the use of $40 for 3 months, at a yearly rate of 7% ?

9. What is the allowance for the use of $90 for 2 months, at a yearly rate of 6% ?

10. In computing the allowance for the use of money, a month is commonly regarded as how many days? Ans. 30 days.

11. What is the allowance for the use of $200 for 1 month 20 days, at a yearly rate of 6% ?

SOLUTION. The allowance for the use of $200 for 1 year is $12; hence, for 1 month, or of a year, it is 1⁄2 of $12, or $1, and for 20 days, or of a month, it is of $1, or $.66}; $1 and $.663 is $1.663, the allowance required.

12. What is the allowance for the use of $100 for 2 months 15 days, at a yearly rate of 8% ?

13. What is the allowance for the use of $300 for 1 month 10 days, at a yearly rate of 5% ?

14. What is the allowance for the use of $120 for 1 year 4 months 6 days, at a yearly rate of 5% ?

15. What is the allowance for the use of $200 for 2 years 5 months 15 days, at a yearly rate of 12%? At a yearly rate of 163%?

DEFINITIONS.

424. Interest is an allowance for the use of money or its equivalent.

425. The Principal is the sum for the use of which interest is allowed.

426. The Rate of Interest is the rate per cent. of the principal allowed for its use for one year.

427. The Amount is the sum of the principal and interest.

WRITTEN EXERCISES.

428.-1. What is the interest of $345.50 for 3 years 3 months, at 6% ?

$5.18. The interest for 3 years 3 months is $62.19+$5.184, or $67.37.

2. What is the interest of $500 for 5 years 6 months, at 7% ?

3. What is the interest of $750 for 4 years 5 months, at 8% ?

4. What is the interest of $840 for 3 years 4 months, at 6% ?

5. What is the interest of $920 for 4 years 2 months, at 5% ?

6. What is the amount of $450 for 7 months 20 days,

7. What is the amount of $600 for 5 months 12 days, at 7% ?

8. What is the amount of $720 for 2 months 3 days, at 6% ?

9. What is the interest of $5000 for 25 days, at 8% ? 10. What is the interest of $4200 for 18 days, at 6% ?

429. Rules for Computing Interest.-Multiply the principal by the rate of interest expressed decimally, and that product by the time expressed in years.

If there be months or days, find the interest for the number of months, by taking fractional parts of a year's interest; and for the number of days, by taking fractional parts of a month's interest.

To find the amount, add the principal and interest.

PROBLEMS.

430.-What is the interest of—

1. $1800 for 3 years 9 months, at 7%?
2. $34.50 for 1 year 6 months, at 6% ?
3. $75.50 for 6 years 11 months, at 8%?
4. $5600 for 4 years 5 months, at 5% ?
5. $8000 for 2 years 2 months, at 4%?
6. $10000 for 15 years 1 month, at 34%?
7. $240 for 10 months 6 days, at 9%?
8. $6450 for 3 months 3 days, at 10%?
9. $65.40 for 1 month 24 days, at 6%?

10. What is the amount of $725 for 1 year 6 months 10 days, at 8%?

11. What is the amount of $830 for 2 years 3 months 27 days, at 7%?

12. What is the amount of $300 for 18 days, at 6% ? 13. What is the interest of $407.60 from Jan. 1, 1869, to April 1, 1871, at 6%?

14. What is the amount of $1000 from May 15, 1870, to October 18, 1871, at 7%?

15. What is the amount of $1200 from February 1, 1871, to November 1, 1872, at 8% ?

431. TEST QUESTIONS.-1. What is any per cent. of a number? What is the rate per cent.? The base? What is percentage?

2. How do you find any per cent. of a number? The rate per cent. a given percentage is of a base?

3. What is interest? The principal? The rate of interest? The amount? How do you compute interest?