16. $725.40 for 5 mos. 27 dys., at 51%.

17. $547.60 from Feb. 20 to Dec. 5, at 31%.

18. $1750 from May 5, 1884, to June 21, 1885, at 51%. 19. $1517 from Jan. 5 to July 1, at 41%.

20. $476.50 from July 5, 1884, to Feb. 9, 1885, at 4%. 21. $319.20 from April 7 to Aug. 31, at 31%.

22. $6460 from June 15, 1883, to May 7, 1885, at 41%. 23. $150 from Aug. 5, 1883, to March 17, 1885, at 7%. 24. $527.20 from Jan. 1 to Nov. 20, at 41%.

25. $1250 from Nov. 15, 1884, to March 1, 1885, at 5%. 26. $624.36 from March 5 to Dec. 20, at 7%.

Find the amount of:

27. $1100 for 3 yrs. 4 mos., at 5%.

28. $1290.50 for 60 dys., at 6%.

29. $1275 for 3 yrs. 2 mos. 15 dys., at 8%.

30. $250.80 for 10 mos. 10 dys., at 31%.

31. $377.65 for 1 yr. 3 mos., at 5%.

32. $7234.25 for 22 yrs. 2 mos. 20 dys., at 41%.

33. $6130 from May 6 to Oct. 24, at 33%.

34. $258.85 from March 6 to June 24, at 5%.

35. $25.62 for 33 dys., at 6%.

36. $85.85 for 1 yr. 7 mos. 21 dys., at 6%.

37. $600 for 93 dys., at 4%.

38. $350 from Sept. 21, 1884, to March 5, 1885, at 4%.

39. $1226 from Oct. 4, 1884, to May 6, 1885, at 5%.

40. $342.42 from Feb. 5, 1884, to March 15, 1885, at 7%. 41. $360.50 from Aug. 1, 1884, to March 3, 1885, at 61%. 42. $504.25 from Jan. 8 to March 10, at 61%.

43. $1240 from Mar. 3 to Aug. 28, at 7%.

NOTE. In business, a year is reckoned at 360 days in computing interest for a time less than a year expressed in months and days; hence the interest is or too great. But national governments take the number of days between the two given dates, and reckon for the interest such a part of a year's interest as this number of days is of 365 days.

222. It is often required to find the rate, time, or principal, when two of these and the interest (or amount) are given.

223. When the principal, interest (or amount), and time are given, to find the rate per cent.

At what rate per cent will $320 produce $48 in 3 yrs.?

Interest on $320 for 3 yrs. is $48.

Interest on $320 for 1 yr. is } of $48.

Interest on $1 for 1 yr. is

But $0.055% of $1.

of of $48 = $0.05.

5%. Ans.

At what rate per cent will $8000 amount to $9277.78

Find the rate per cent:

Ex. 143.

1. When the interest on $500 for 1 yr. 6 mos. is $67.50. 2. When the interest on $250 for 2 yrs. is $52.50. 3. When $500 amount to $754 in 9 yrs.

4. When the interest on $725 for 12 yrs. is $141.371⁄2. 5. When $880 amount to $899.25 for 7 mos.

6. When the interest on $424 for 2 yrs. 6 mos. is $26.50. 7. When the interest on $255.50 from April 1 to June 20 is $2.80.

8. When $175 amount to $203.35 for 3 yrs. 7 mos. 6 dys. 9. When a sum of money is doubled in 16 yrs.

10. When an investment for 6 yrs. produces a sum equal to of the capital.

224. When the principal, interest (or amount), and rate per cent are given, to find the time.

In what time will the interest on $793.87 be $11.96, at 51%?

Interest on $793.875 at 5% for 1 yr.

Therefore the number of years will be

And 0.274 yr. 3 mos. 9 dys.

=

=

$43.663. 11.965

0.274.

43.663

3 mos. 9 dys. Ans.

Ex. 144.

Find the time in which :

1. The interest on $225 will be $36, at 4%.

2. $440 will amount to $505.45, at 41%.

3. $250 will double itself, at 21%.

4. $225 will amount to $256.50, at 31%.
5. $50 will amount to $85, at 6%.

6. The interest on $4260 will be $873.30, at 6%.
7. $1005.34 will amount to $1156.14, at 41%.
8. $1587.75 will amount to $1611.68, at 51%.

9. A sum of money will double itself, at 6%. 10. $1000 will amount to $1125, at 4%.

225. When the interest, time, and rate are given, to find the principal.

What principal will in 8 yrs. 6 mos. produce $100 interest, at 5%?

Find the principal that will:

1. Produce $180 interest in 3 yrs., at 4%.

2. Produce $189 interest in 3 yrs., at 61%.

3. Produce $3493.20 interest in 3 yrs. 5 mos., at 6%. 4. Produce $10.70 interest in 5 mos., at 4%. 5. Produce $75.40 interest in 3 yrs. 4 mos., at 41%. 6. Produce $75.05 interest in 3 mos. 2 dys., at 41%.

7. Produce $1746.60 interest in 3 yrs. 5 mos., at 6%. 8. Produce $64.46 interest in 6 yrs., at 41%.

9. Produce $80.621 interest in 3 yrs. 9 mos., at 4%.

10. Produce $669.64 interest in 2 yrs. 7 mos. 24 dys., at 6%.

226. When the amount, time, and rate are given, to find the principal.

Find the principal that will amount to $748.12 in 3 yrs. 6 mos., at 4%.

3 yrs. 6 mos. = 3 yrs.

Let the principal be represented by 100.

The interest will be represented by 3 × 4 = 14.
The amount will be represented by 100 + 14 = 114.
Hence the principal = 194 of $748.125 = $656.25.
$656.25. Ans.

Ex. 146.

Find the principal that will amount:

1. To $1680 in 3 yrs., at 4%.

2. To $962 in 4 yrs., at 41%.

3. To $725.47 in 2 yrs. 3 mos., at 31%. 4. To $3215.83 in 4 yrs. 6 mos., at 3%. 5. To $595.20 in 8 mos., at 6%.

6. To $1275.75 in 1 yr. 1 mo., at 5%.

7. To $2053.32 in 3 yrs. 5 mos., at 6%.

8. To $131.88 in 2 yrs. 11 mos. 15 dys., at 6%. 9. To $37.02 in 2 yrs. 3 mos. 18 dys., at 5%. 10. To $2359.38 in 2 yrs. 7 mos. 24 dys., at 41%.