valorem duty is 20%; the specific duty is $0.20. Find the gross value of a single yard.

24. The specific duty is $0.44 per lb. ; the ad valorem duty is 60%; the gross cost is $244. Find the invoice price of 100 lb.

25. The ad valorem duty is 50%; the invoice price is $500; the selling price at a profit of 25% is $1000 on 100 lb. Find the gross value and the specific duty.

INTEREST.

1. Interest is money paid for the use of money, and depends both upon a certain rate per cent. and the length of time the money is in use.

2. The money used is the Principal (Base).
3. The interest for one year is the Percentage.

4. The interest for a longer or a shorter time than one year is the product of the percentage and the time expressed in years or in the fraction of a year.

5. The time, when expressed in months, must be divided by 12; when expressed in days, by 360.

6. Since percentage equals the product of principal (base) and rate, we have the following formulæ :

1. Interest= Principal X Rate x Years;
or, (Int. = Pr. X R. X Y.).

Principal X Rate x Months.
2. Interest

12 Pr. X R. X mo.

; * mo.). 12

or, (Int.

3. Interest

Principal X Rate x Days.

360
Pr. X R. X da.).

X
360

or, (Int.

MODEL SOLUTIONS. 1. What is the interest of $550 at 5% for 4 yr.?

Process.

Int. = Pr. X R. X Y.= $550 X .05 X 4= $110.

Explanation. Since the int. is required for exactly 4 yr., we use the formula, Int. = Pr. X R. X Y.= $550 X .05 X 4 = $110.

Or, we may explain thus :

Since the rate per cent. is 5, the int. for 1 yr. .05 of $550 = $27.50. Since the int. for 1 yr. $27.50, the int. for 4 yr. 4 times $27.50 $110.

2. What is the interest of $500 for 5 yr, and 2 mo. at 6% ?

Process.

5 yr. 2 mo. =

62 mo.

31 Pr. x R. X mo. 500 x .Ø6 x 62 Int. =

= 5 X 31 = $155. 12

12
200

Pr. X R. X mo.

12

Explanation. Since the int. is required for 62 mo., we use the formula, Int. =

By cancellation we have 5 X 31 = $155. Or,

500 X .06 X 62

12

The int. of $500 for 1 yr. at 1% $5.00; at 6%, therefore, it = $5 X

31
$5 X 6
6, for 1 yr.; for 1 mo. it

; for 62 mo. it
$5 X 6 X 62

$155. 12

12

3. What is the interest of $222.50 for 10 yr. 8 mo. 21 da. at 3% ?

10 yr.

8 mo.

=

Process. = 120 mo.

Pr. X R. X mo. 8 mo. =

128.7 mo.
Int.

12
21 da.

0.7 mo. .55625 222 30 x .Ø3 x 128.7

.55625 x 128.7 = $71.59.

X 12

400 Or, 10 yr. =3600 da.

Pr. X R. X da. 8 mo. = 240 da. - 3861 da. Int.

360 21 da. 21 da. 222.50 x .03 X 3861

.89 x 1287 by cancellation =

$71.59. 360

16 NOTE.—The work may be simplified by removing decimals be celling.

EXERCISES.

=

=

can

1. Find the interest of :

1. $100 for 1 yr. at 8%. 6. $600 for 6 yr. at 10%. 2. $200 for 2 yr. at 6%. 7. $700 for 7 yr. at 7%. 3. $300 for 3 yr. at 10%. 8. $800 for 8 yr. at 6%. 4. $400 for 4 yr. at 7%. 9. $900 for 9 yr. at 6%. 5. $500 for 5 yr. at 6%. 10. $1000 for 10 yr. at 8%.

Pr. X R. x mo.
Int.

12 2. Find the interest of:

1. $590 for 3 yr. 7 mo. at 7%.
2. $600 for 4 yr. 11 mo. at 10%.

4
3. $830 for 5 yr. 10 mo. at 6%.
4. $950 for 5 yr. 9 mo. at 6%.
5. $1070 for 6 yr. 11 mo. at 6%.
6. $470 for 3 yr. 8 mo, at 10%.
7. $2359 for 4 yr. 7 mo. at 12%.

8. $3597 for 6 yr. 9 mo. at 8%.
9. $2300 for 4 yr. 6 mo. at 6%.

10. $7000 for 1 yr. 7 mo. at 7%. 3. Find the interest of:

1. $10 for 1 yr. 1 mo. 3 da at 5%.
2. $121 for 2 yr. 2 mo. 6 da. at 6%.
3. $25.16 for 3 yr. 3 mo. 9 da. at 6%.
4. $36.24 for 4 yr. 4 mo. 12 da. at 7%.
5. $48.20 for 5 yr. 5 mo. 15 da. at 7%.
6. $2000 for 6 yr. 6 mo. 18 da. at 6%.
7. $590.50 for 7 yr. 7 mo. 21 da, at 6%.
8. $640.82 for 8 yr. 8 mo. 24 da. at 10%.
9. $725.83 for 9 yr. 9 mo. 27 da. at 6%.
10. $618.24 for 10 yr. 10 mo. 3 da. at 6%.

Int.

Pr. X R. X da.

360 4. Find the interest of:

1. $7000 for 1 yr. 6 mo. 7 da. at 3%.
2. $8300 for 2 yr. 5 mo. 5 da. at 4%.
3. $670 for 4 yr. 8 mo. 8 da. at 41%.
4. $950 for 6 yr. 6 mo. 10 da. at 5%.
5. $500 for 8 yr. 7 mo. 11 da. at 51%.
6. $700 for 8 yr. 6 mo. 13 da. at 6%.
7. $3000 for 5 yr. 8 mo. 14 da. at 7%.
8. $600 for 4 yr. 9 mo. 16 da. at 8%.
9. $300 for 4 yr. 8 mo. 17 da. at 9%.
10. $536 for 3 yr. 10 mo. 19 da. at 10%.

The Amount equals the Principal plus the Interest. 1. Find the amount of:

1. $1 for 3 yr. 3 mo. 3 da. at 6%.
2. $125 for 4 yr. 4 mo. 4 da. at 6%.

3. $24.50 for 5 yr. 5 mo. 5 da. at 7%.
4. $1000 for 6 yr. 6 mo. 6 da. at 10%.

5. $280.75 for 7 yr. 7 mo. 7 da. at 6%. 2. Find the interest of:

1. $2000 for 5 mo at 31%.
2. $6030 for 15 da. at 41%.
3. $700 for 6 mo. 20 da. at 51%.
4. $60.70 for 11 mo. 27 da. at 61%.
5. $400 for 30 da. at 6%.
6. $1670 from April 1 to Dec. 25 at 7%.
7. $4440 from Feb. 4 to June 8 at 5%.
8. $1060 from April 13, 1897, to Dec. 21, 1898, at

41%

=

Six Per Cent. Method.

MODEL SOLUTION. At 6% the interest of $1.00 for one year $.06; for one month 12

t of $.06 = $.00); for one day 3o of $.002 $.0001 Hence, writing 6 cents for every year, 1 a cent for every month, and 1 of a mill for every day, we have the formula :

$.06

X yr.
Int.
Pr. X

.00 X mo. add.

.0002 x da. What is the interest of $236 for 3 yr. 4 mo. 18 da., at 6% ?

Process.

.18
Int. $236 x .02 236 x .203= $47.91.

2