Add the following as on page 20. Write down the results only. Do not copy the example. Add the following as in § 28. Do not copy the examples. Write down results only. 10. 41 + 64 + 31 + 14 + 71 + 24 + 62. 11. 1920 +46 + 39 + 78 + 22 + 61. 12. 26 + 35 + 19 + 17 + 66 + 42 + 18. 13. 4739 +62 +45 +20 + 76 + 33. 14. 1876 + 23 + 48 + 18 +81 + 46. 15. 42 + 91 + 27 + 15.+ 56 + 73 + 38. 16. 6587 +23+39 +22 + 38 + 17. 17. 91 + 15 + 26 + 14 + 17 + 83 + 67. 18. 76 + 23 + 10 + 23 + 93 + 77 + 29. 19. 28 + 55 + 26 + 95 + 49 + 26 + 35. 20. 1721 +36 +68+ 38 +19 +13. CHAPTER III SUBTRACTION 31. Definition of Subtraction. -Subtraction is the process of finding · how much must be added to a given number to make the sum equal to another given number. Thus: "How much must be added to 30 to make the sum 70?" is a problem in subtraction. 32. Minuend, Subtrahend, Remainder. - The given sum is called the minuend and the other given number is called the subtrahend. The number to be found is called the remainder. The sign indicates subtraction and is read minus or less. The number before the sign is the minuend, and the number after it is the subtrahend. The expression" 70 - 30 = 40," is read " 70 minus 30 equals 40." 33. Other Definitions of Subtraction. We also say that "Subtraction is the process of finding the difference between two numbers," or that "it consists in finding how much is left when one number is taken from another number.” 66 All these definitions of subtraction amount to the same thing. Thus we may ask, "What is the difference between 30 and 70? or How much must be added to 30 to make 70?" or "How much is left when 30 is taken from 70?" In this book subtraction will be regarded as the process of finding how much must be added to one number, the subtrahend, to give another number, the minuend. The process of subtraction will be performed by actually adding enough to the subtrahend to produce the minuend. This method of subtraction has the advantage that it connects more directly with addition than the other methods. 34. Uses of Subtraction. Subtraction is used constantly in busi"Making change" is one of its simplest uses. Finding balances of accounts, gains or losses, etc., all involve subtraction. ness. Subtract the following: ORAL EXERCISES Read the first example 148+ 6 or 14, 8, 6. 86 or 14, 8, 6. After a little practice the remainder should be seen at a glance. Read rapidly, giving the difference between the numbers in each of the following pairs. Read the first example 11 = 3 + 8 or simply 11, 3, 8. After a little practice the differences should be seen at a glance and only the differences given. 35. Subtrahend Written above the Minuend. Sometimes the smaller number (the subtrahend) is written above the larger (the minuend). It is best to get some practice in finding the difference between numbers written this way, since in many cases that will save the work of copying. ORAL EXERCISES In the following give the difference between the numbers above the line. Read the first example: 179+ 8 or simply 17, 9, 8, or better still, read the difference at a mere glance. In the following sequences of numbers read the difference between each number and the one which follows it. Thus in 4, 9, 15, 23, 29, 37, 45, 53, 68, 81, read 5, 6, 8, 6, 8, 8, 8, 15, 13. 1. 6, 8, 12, 19, 21, 29, 40, 51, 59, 67, 73, 82, 95, 100. 2. 14, 19, 31, 39, 47, 53, 64, 71, 83, 84, 96, 100. 3. 7, 19, 27, 41, 53, 62, 73, 85, 100. 4. 9, 14, 24, 32, 43, 53, 62, 70, 79, 89, 100. 5. 15, 27, 34, 45, 54, 63, 75, 82, 93, 100 6. 8, 19, 31, 43, 52, 65, 74, 81, 93, 100. |