719468.24 7145297.54 957421.643 536827.78 235010.33 203941.41 319025.14 615521.21 753015.03 875354.02 17. Before attempting to find the sum in each of the following exercises, arrange the numbers to be added so that units of the same order will fall in the same vertical column. Ex. 20. Add the following numbers: 1. 947,347,856.45; 92,036.008; 453.934,7; 57,328; 964,832 .754; 327.834,96. 2. 3,845.95; 978.070,8; 76,829.345; 7,006.934; 582.796,8; 1, 324.85; 319,587.946. 3. 74,166.42; 89,991.924; 1,796.041,3; 46,871.049; 3,586.24. 4. 1,796.2; 3,911.000,08; 69,422.001; 211,664.835,12; 24,410 .67; 444,256.25. 5. 2,256,884.1; 371,235.265; 54,476.482,6; 7,123,157,38; 48, 629.777,5; 248.841; 94.673,771. 6. 3,000,126.7; 47,924.500,1; 497,300,000.000,2; 479.624; 2, 567,864.05; 1,432,699.006; 38,452,840.1. 7. 1,045,061.1; 325.42; 956,427.854; 68,539.431; 2,000,000 .903; 145,769.74; 9,000,101.000,472. 8. 161,893.17; 87,456.6; 255.329,46; 857,437.954,2; 89,742, 226,432.104; 25,354.100,07. 9. 5,835,205.20; 600,320.6; 50,208.700; 320,679.50; 7,786, 825.009; 25.02; 6,328.65; 845,936.020. 10. 45,675.25; 9,236.030; 4,289.25; 2.658.723; 3,258.63; 241 .720; 7,933.940. 11. 43,250.963; 6,050.02; 689.003; 9.02; 560.28; 33,675.3; 4, 589.300. 12. 67,933.250; 7,458.678; 75,876.98; 53,985.07; 6,783.25; 795.05; 55.67; 3,678.95. 13. 5,679.456; 542.06; 32.458; 9,458.965; 523.76; 1,865.020; 468.95. 14. 935,463.002; 46,893.01; 365,840.250; 46,270.30; 968,530 .235; 75,963.24; 540.685. 15. 25,940.25; 6,586.04; 75,900.45; 43,001.50; 6,948.06; 40, 630.78; 7,985.95. 16. 83,250.45; 9,285.36; 80,520.99; 4,368.25; 28,395.48; 44, 325.789; 75,982.75. Mental Addition. One may have occasion to add mentally numbers of EXPLANATIONS. 1. We are to add 350, 392, 478, 555, 197, 324, Commencing with the left-hand column and 2. We are to add 7056, 8922, 1090, 2840, 3725, 3128 32620 Commencing with the left-hand column and 18. To Subtract when the Subtrahend or the Remainder. is Greater than 9. We are to subtract 4863 from 6749. 3 units from 9 units leave how many units? Can we subtract 6 tens from 4 tens? 6749 4863 1886 Suppose that we add ten tens to the minuend. How many hundreds must we add to the subtrahend to counterbalance this addition? 6 tens from 14 tens leave how many tens? How many hundreds have we to subtract from the 7 hundreds? Can we subtract 9 hundreds from 7 hundreds? Suppose that we add ten hundreds to the minuend? How many thousands must we add to the subtrahend to counterbalance this addition? 9 hundreds from 17 hundreds leave how many hundreds? How many thousands have we to subtract from the 6 thousands? 5 thousands from 6 thousands leave how many thousands? 4863 subtracted from 6749 leaves, then, what remainder? Ex. 1. Subtract 2364 from 6876. SOLUTIONS. (1) (2) (3) 6876 87.48 6849 2364 32.92 4963 4512 54.56 1886 EXPLANATIONS. Ex. 1. We are to subtract 2364 from 6876. For convenience we so write the subtrahend that each of its orders will fall under the corresponding order of the minuend. 4 units from 6 units leave 2 units, 6 tens from 7 tens leave 1 ten 3 hundreds from 8 hundreds leave 5 hundreds, and 2 thousands from 6 thousands leave 4 thousands. Therefore, 2364 subtracted from 6876 leaves 4 thousands, 5 hundreds, 1 ten, and 2 units, or 4512. Ex. 2. We are to subtract 32.92 from 87.48. 2 hundredths from 8 hundredths leave 6 hundredths. We cannot subtract 9 tenths from 4 tenths. We therefore add 10 tenths to the minuend. The effect of this addition upon the remainder we must counterbalance by adding 1 unit to the subtrahend. 9 tenths from 14 tenths leave 5 tenths, 3 units from 7 units leave 4 units, and 3 tens from 8 tens leave 5 tens. Therefore, 32.92 subtracted from 87.47 leaves 54.56. Ex. 3. Explain the solution of Ex. 3. |