20. What sum added to the sum of £.7854 .85s. and .76842d will make £2? Ans. £1.3s. 4.53558d. 21. Find the value of 0.05 of £3 10s., and express the result as the decimal of a £. Ans. 3s. 6d. and .175£.

22. Reduce the following expression to a decimal, having seven places.

RULE OF THREE IN DECIMALS.

RULE. Reduce the given quantities into decimals, and proceed as in whole numbers. When repetends occur, reduce them to their equivalent vulgar fractions, as in Example 2nd.

EXAMPLES.

1. Bought 1 yd. 3 qr. of cloth for £1 2s. 6d. ; what is the value of 17 yds. 2 qrs. ?

4)3.0

1.75

12)6.0

20)2.5

1,125

4)2.0

17.5

£. s.

11 5 Ans.

2. Bought sugar at £2 17s. 6d. per cwt.; what is the

value of 5 cwt. 2 qrs. 7 lb. ?

NOTE-For practice under this rule, the student may work, Decimally, the different Examples given in the Rule of Three Direct, Inverse, and the Double Rule of Three.

INTEREST.

INTEREST is money paid for the use of money; or, it is a sum of money paid by the borrower to the lender, for the use of his money. It is divided into Simple and Compound.

SIMPLE INTEREST.

The Principal is the sum of money lent. The Rate per Cent. or per £100, is the sum agreed upon between the borrower and the lender, which the former is to pay to the latter, for the use of £100, for one year :-Thus 5 per cent. per annum, means, that the borrower is to pay to the lender £5 for having the use of his £100 one year; 4 per cent. per annum means that £4 10s. are to be paid for the use of £100 for one year; 4 per cent. per annum means, that £4 are to be paid for the use of £100 for one year; 3 per cent. per annum, that £3 10s. are to be paid, and so on.

When no rate per cent. is agreed upon, 5 per cent. per annum is always understood.

The Amount is the principal and interest added together.

CASE I. To find the interest and amount of any sum of money, for one year, or any given number of years.

RULE. AS £100 are to the rate per Cent., so is the given sum to the interest for one year; multiply this interest by the number of years, and the product will be the interest required.

Or, multiply the given sum by the rate per cent., and this product by the number of years; divide this last product by 100, and the quotient will be the interest required.

NOTE. Dividing by 100 is only cutting off two figures from the right hand.

Or, if the rate per cent. be any aliquot part of 100, divide the given sum by such aliquot part, and the quotient will be the interest for one year. If the product of the rate per cent. and time be any aliquot part of 100, divide the given sum by such aliquot part, and the quotient, will be the interest required. See the following table :

1. What is the interest of £365 12s. 6d. for one year, at

5

per cent.

per annum ?

2. What is the interest of £254 17s. 6d. for 5 years, at 4

per cent. per annum?

6,00 3. What is the interest of £48 per cent.?

4. What is the amount of £325 per cent. per annum ?

5. What is the interest of £349 cent. per annum?

6. What is the amount of £320 5 per cent. per annum ?

15s

Ans. £50 19s. 6d.

9d. for 1 year, at 5 Ans. £2 8s. 91d. 15s. 5d. for 4 years, at 5

Ans. £390 18s. 6d. 10s. for 3 years, at 4 per

Ans. £48 18s. 7d. 12s. 6d. for 5 years, at Ans. £408 15s. 114d. 15s. 34d. for 4 years, at Ans. £264 10s. lad.

7. What is the interest of £1429 £4 12s. 6d. or 4 per cent. per annum? 8. What is the interest of £325 17s. 6d. for 43 years, at £4 17s. 6d., or 47 per cent. per annum? Ans. £75

9s. 24d. 9. What is the interest of £126 17s. 6d. for 7 years, at 3 per cent. per annum? Ans. £32 3s. 10 d. 10. What is the interest of 320 moidores, for 5 years, at 5 per cent. per annum ? Ans. £108.

11. What is the interest of of of £357 14s. 5‡d., † of ? of £1000, and 3 of 160 quarter guineas, for one year, at 5 per cent. per annum? Ans. £25 2s. 43d. 12. What is the amount of 367 crowns, of of £17, and of of 27 moidores, at 5 per cent. per annum, for 2 years? Ans. £138 4s. 11⁄2d.

CASE II.-To find the interest for years and months.

RULE. Find the interest for the years, as in Case 1st, and take parts for the months; add them together, and their sum will be the interest required.

EXAMPLES.

1. What is the interest of £320 12s. 6d. for 3 years and 8 months, at 5 per cent. per annum?

2. What is the interest of £125 12s. 6d. for 2 years and

9 months, at 4 per cent. per annum?

3. What is the interest of £148 7 months, at 5 per cent. per annum ?

4. Lent my friend £74 15s. on the much do I want this day, July the interest?

5. What is the interest of £374 months, at 4 per cent. per annum ?

Ans. £15 10s. 11d.

6s.

8d. for 2 years and

Ans. £19 3s. 24d.

1st

of January. How

1st.

for principal and

Ans. £76 12s. 4 d.

15s.

for 1 year and 10

Ans. £32 12s. 81d.

6. Lent my friend £327 10s. on the 1st of January, 1841, at 5 per cent. per annum. How much do I want for principal and interest on the 1st of May, 1842? Ans. £349 6s. 8d.