MENTAL ARITHMETIC: SUBTRACTION PROBLEMS To see the answer, pass your mouse over the colored area. 11. a) Explain why 41 − 35 = 6. Because 35 plus 6 is 41. 12. Practice the following. Do not count on your fingers! 12. 2 + 7 = 9 1 + 5 = 6 2 + 3 = 5 2 + 6 = 8 12. 6 + 2 = 8 7 + 2 = 9 2 + 5 = 7 3 + 6 = 9 12. 3 + 4 = 7 5 + 4 = 9 3 + 2 = 5 1 + 7 = 8 12. 4 + 2 = 6 2 + 4 = 6 1 + 3 = 4 5 + 2 = 7 12. 5 + 3 = 8 1 + 4 = 5 5 + 2 = 7 6 + 3 = 9 12. 4 + 3 = 7 4 + 5 = 9 2 + 2 = 4 3 + 3 = 6 12. 1 + 8 = 9 1 + 5 = 6 3 + 5 = 8 1 + 2 = 3 13. Calculate each column mentally by adding to the smaller number.
14. What number must you add? 12. 8 + 6 = 14 8 + 5 = 13 7 + 9 = 16 8 + 3 = 11 12. 2 + 9 = 11 4 + 8 = 12 9 + 8 = 17 7 + 6 = 13 12. 5 + 7 = 12 9 + 7 = 16 6 + 5 = 11 5 + 6 = 11 12. 6 + 9 = 15 5 + 9 = 14 5 + 8 = 13 8 + 9 = 17 12. 9 + 4 = 13 6 + 6 = 12 8 + 7 = 15 6 + 8 = 14 12. 7 + 5 = 12 4 + 9 = 13 9 + 3 = 12 4 + 7 = 11 12. 3 + 8 = 11 7 + 8 = 15 9 + 2 = 11 8 + 4 = 12 12. 6 + 7 = 13 7 + 4 = 11 9 + 5 = 14 3 + 9 = 12 15. What number must you add to the smaller number? 120 − 90 30 1900 − 1200 700 126 − 90 36 1800 − 1400 400 135 − 90 45 1842 − 1400 442 124 − 80 44 1986 − 1600 386 138 − 80 58 2004 − 1500 504 146 − 80 66 2110 − 1700 410 The complement to 10
17. More complements to 10.
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18. Calculate mentally.
19. Subtracting a one-digit number. Break off from the smaller Illustrate that in writing. 61 − 3 = 61 − 1 − 2 = 60 − 2 = 58 93 − 4 = 93 − 3 − 1 = 90 − 1 = 89 10. Calculate mentally.
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