3. What is the interest of $60 for 5 months, at 1% a month? 4. What is the interest of $200 for 4 months, at 9% per annum? ANALYSIS.-9% of $200 is $18, which is the interest for 1 year; and the interest for 4 months is or 1⁄2 of $18 = $6. 5. At 2% a month, what will I pay for the use of $100 for 6 months? At 12% per annum? 6. What is the interest of $400 for 6 months, at 6% per annum? At 1% a month? 7. At 5% a year for 10 years, what part of the principal is equal to the interest? ANALYSIS.-At 5%, 15 of the principal = the interest for 1 year; and for 10 years, 10 times or of the principal = the interest. 8. At 6% per annum for 16 years, what part of the principal equals the interest? 9. What is the interest of $500 for 1 year, at 10%? For 10 years? 10. I borrow $200 from a friend for 1 year, at 6%; what do I owe him at the end of the year? 11. What is the interest of $50 for 2 yr. 3 mo., at 8% ? What is the amount? 12. I place $600 in a savings bank, which pays 4% per annum; what is due me at the end of one year? 13. Find the amount of $100 for 2 yr. 6 mo., at 4%. At 5%. At 6%. At 10%. 14. Find the interest of $60, at 6%, for 2 months. For 3 months. For 6 months. For 8 months. For 9 months. 15. I loan $500 for 1 yr. 4 mo., at 6%; what amount is due me at the expiration of that time? 16. What is the interest of 1 dollar for 20 years, at 5% ? WRITTEN EXERCISES. 1. What is the interest of $200.25 for 3 years, 5 2. What is the amount of $420 for 2 yr. 3 mo. 15 da., Note. It is customary among business men to consider 30 days as a month, and 12 months as a year. In transactions with the U. S. Government, however, 365 days are considered a year. RULE. Multiply the principal by the rate per cent. expressed decimally, and the product will be the interest for 1 year. If the time is in years and months, multiply this product by the time expressed in years and the fraction of a year. If the time is in years, months, and days, take 12 of the year's interest, and multiply it by the time expressed in months and the fraction of a month. 3. What is the interest of $180.50 for 2 yr. 8 mo., at 8%? 4. What is the interest of $1200 for 3 yr. 4 mo. 15 da., at 7%? 5. What is the interest of $860.90 for 11 mo. 10 da., at 5%? 6. What is the amount of $800 for 5 yr. 6 mo. 20 da., at 6%? 7. What is the amount of $100 for 8 mo. 19 da., at 5%? 3 mo. 8. What is the interest of $50 for 1 yr. 10 mo., at 41%? 9. What is the interest of $1.00 for 2 5 da., at 6%? What is the amount? yr. 10. What is the interest of $100 for 2 yr. 3 mo. 5 da., at 6%? What is the amount? 11. I borrow $1000, at 2% a month; how much do I owe at the end of 6 mo. 9 da.? 12. I loaned $580.75 from January 1, 1874, to January 15, 1876, at 6%; what amount was then due me? 13. What is the interest, at 7%, on $1200, from July 6, 1873, to October 10, 1876? 14. What is the amount of $750.60 for 1 yr. 1 mo. 1 da., at 5%? 15. What is the interest of $100, at 6%, for 16 yr. 8 mo.? At 5%, for 20 years? 16. What is the interest of $850, at 8%, for 12 yr. 6 mo.? At 10%, for 10 years? 17. I bought a house for $4000, and agreed to pay for it in 1 year and 9 months, with 41% interest; what amount had I to pay? 18. What is the difference between the interest of $500, +6%, for 10 years, and at 10%, for 6 years? BUSINESS METHOD. ORAL EXERCISES. 1. What is the interest of $1 for 1 year, at 6%? For 1 day? ANALYSIS. The interest of $1 for 1 year, at 6%, is 6 cents, and for 1 day, or of a year, it is of 6 cents of a cent. 2. If the interest of $1 for 1 day, at 6%, is cent, what is the interest of $1 for 30 days? days? For 90 days? For 180 days? 3. If the interest of $1 for 1 day, at 6%, is what is the interest of $20 for 1 day, at 6%? Of $120? Of $240? Of $300? of a For 60 of a cent, Of $60? 4. What is the interest of $30 for 120 days, at 6% ? ANALYSIS.—If the interest of $1 for 1 day is of a cent, the interest of $30 for 1 day is 30 times of a cent = 88 or cent. If the interest of $30 for 1 day iscent, for 120 days it is 120 times cent=120 or 60 cents. What is the interest, at 6%, of — 5. $120 for 90 days? 8. $240 for 50 days? For 20 days? 9. If the interest on a certain sum, at 6%, is $72, what would be the interest on the same sum, for the same time, at 5%? ANALYSIS.—If the interest at 6% = $72, the interest at 5% = of $72-$60. 10. What is the interest of $360 for 20 days, at 6%? At 3%? At 4%? At 7%? At 8%? At 10%? 11. What is the interest of $360 for 60 days, at 6%? WRITTEN EXERCISES. 1. What is the interest of $400 for 1 yr. 6 mo. 21 da., at 6%? 1 yr. 6 mo. 21 da. = 561 days. ANALYSIS. As the interest of $1 for 1 day, at 6%, is of a cent, the interest of $400 for 1 day is 400 times of a cent= 400 cents, and for 561 days it is 561 times 400=3740 cents, or $37.40. 60 Note.-It will be seen in the above operation that the number denoting the dollars has been multiplied by the number denoting the days, and the result divided by 60, giving the answer in cents; now, as of a cent is of a dollar, dividing by 6000 would have given the answer in dollars; the general practice, however, is to divide by 6, pointing off three figures if there are only dollars in the dividend, and five figures if there are dollars and cents, thus giving the answer in $400 × 561 224.400 dollars and cents. Thus, 6 6000 RULE. = = $37.40. Multiply the principal by the number denoting the time in days, and divide the product by 6, pointing off three figures in the quotient when the principal is in dollars only, and five figures when there are cents in the principal. Note. For any other rate %, multiply the interest, at 6%, by the given rate, and divide by 6. 2. What is the interest of $500 for 84 days, at 6%? 3. What is the amount of $1600 for 60 days, at 6% ? 4. What is the interest of $184.66 for 1 yr. 6 mo. 10 da., at 6%? What is the amount? 5. What is the amount of $1 for 360 days, at 6%? 6. What is the amount of $785.90 for 30 days, at 6%? 7. At 6%, what is the interest of $5000 for 5 yr. 5 mo. 5 da.? What is the amount? |