17. Find the sum of 9 tenths, 18 hundredths, 125 thousandths, 62 ten-thousandths, 165 tenths, and 125 thousand. 18. Find the sum of five, and twenty-four hundredths, eight, and sixty-two ten-thousandths, ninety, and forty-one millionths, two hundred and five, and one thousand three hundred and seven ten-millionths. 19. A wagon cost $25.37, a horse $180.90, a set of harness $10.05, a mowing-machine $85.37, a cow $28.08, and a pair of mules $225.75; what was the entire cost? 20. What is the sum of $25 and 18 cents, $45 and 27 cents, $610 and 39 cents, $250 and 81 cents, and $1001 and 57 cents? SUBTRACTION OF DECIMALS. WRITTEN EXERCISES. 97.-1. Subtract 129.486 from 726.278. PROCESS. 726.278 129.486 596.792, Ans. We write the numbers so that their decimal points are in the same vertical column, and subtract as in whole numbers, placing the decimal point between units and tenths. 24. From 16 hundredths take 16 millionths. 25. From 10.32 take 17 ten-millionths. 26. From four hundred, and four thousandths take four hundred and four thousandths. 27. A farmer bought 102.26 acres of land from A, 140.216 acres from B, 47.025 acres from C, and enough from D to make in all 400 acres; how much did he buy from D? 28. A coal-dealer bought 1020 tons of coal: he sold A 40.025 tons, B 105.008 tons, C 208.125 tons, D 416.375 tons, and E 50.015 tons; how much was left? MULTIPLICATION OF DECIMALS. ORAL EXERCISES. 98.-1. How much is 3 X? 4X.2? 3X.3? 5. How much is Too × 100? .02 × .03? .06 × 04? 6. When tenths are multiplied by tenths, how many decimal places are there in the product? Tenths by hundredths? Tenths by thousandths? Hundredths by hundredths? 99. The product of two decimals contains as many decimal places as there are decimal places in both factors. WRITTEN EXERCISES. 1. Multiply 24.6 by .24. PROCESS. 24.6 .24 984 492 5.904, Ans. 1ST. 246 multiplied by 24 is 5904, but tenths multiplied by hundredths give thousandths; hence the result is 5904 thousandths, or 5.904. Multiply as in whole numbers, and point off as many decimal places in the product as there are in both factors. Prefix ciphers to the product if it does not contain the required number of figures. 23. Multiply 1.080502 by 3.216. 24. Multiply .00432 by .00037. 25. Multiply 8 by .071 by 10. 29. Multiply .42, 3.04, .125, and .826 by .0031. DIVISION OF DECIMALS. ORAL EXERCISES. 100.-1. What is 3? .63? .8÷4? 2. What is 100 1000 ? .48.6? .56 ÷ .7? 3. What is Toooo? .024.8? .072.9? 5. When hundredths are divided by tenths, how many decimal places are there in the quotient? Thousandths by tenths? Thousandths by hundredths? 6. .36 ÷ 9. 7. .42 ÷ 6. 8. .64 ÷ 8. 9. .72 9. 10. .36 .9. | 14. .035 ÷ .7. | 18. .012÷.06. 20. .032 ÷ .08. 21. .054 ÷ .06. 101. The quotient of two decimals contains as many decimal places as those in the dividend exceed those in the divisor. WRITTEN EXERCISES. 1. Divide 2.176 by .34. PROCESS. .34)2.176 204 136 136 1ST. 2176 divided by 34 is 64; but thousandths divided by hundredths give tenths: hence the quotient is 64 tenths, or 6.4. Divide as in whole numbers, and point off as many decimal places in the quotient as those in the dividend exceed those in the divisor. 1. If the number of decimal places in the dividend is less than the number of decimal places in the divisor, make them equal before beginning the division. 2. If the quotient does not contain the required number of decimal places, supply the deficiency by prefixing ciphers. 2. Divide 16.5 by .25; and .29808 by 124.2. 30. Divide .023 by 10. By 100. By 1000. 31. Divide 16000 by .0004. 32. Divide .00016 by 4000. 33. Divide .2952, 99.63, and 1.3653 by .123. 34. Divide 7.1262, .96942, and 54.891 by 3.21. 35. Divide one, and one hundred-millionth by one ten-thousandth. |