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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 137 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.16 + 29 =
  2. 2.36 − 19 =
  3. 3.68 − 9 =
  4. 4.27 + 19 =
  5. 5.835 − 99 =
  6. 6.523 + 99 =
  7. 7.70 − 9 =
  8. 8.387 + 99 =
  9. 9.42 + 29 =
  10. 10.23 + 19 =
  11. 11.15 + 19 =
  12. 12.69 + 9 =
  13. 13.18 − 9 =
  14. 14.80 + 29 =
  15. 15.57 − 19 =
  16. 16.50 − 29 =
  17. 17.33 + 9 =
  18. 18.51 + 29 =
  19. 19.77 + 9 =
  20. 20.45 − 19 =
  21. 21.92 − 19 =
  22. 22.53 − 29 =
  23. 23.43 + 9 =
  24. 24.13 − 9 =
  25. 25.28 + 29 =
  26. 26.68 + 9 =
  27. 27.65 + 19 =
  28. 28.83 − 9 =
  29. 29.35 − 29 =
  30. 30.21 + 9 =
  31. 31.466 + 99 =
  32. 32.63 + 9 =
  33. 33.34 − 9 =
  34. 34.700 + 99 =
  35. 35.77 − 9 =
  36. 36.394 − 99 =
  37. 37.59 + 9 =
  38. 38.782 − 99 =
  39. 39.26 + 29 =
  40. 40.76 − 9 =

Answer key

  1. 45
  2. 17
  3. 59
  4. 46
  5. 736
  6. 622
  7. 61
  8. 486
  9. 71
  10. 42
  11. 34
  12. 78
  13. 9
  14. 109
  15. 38
  16. 21
  17. 42
  18. 80
  19. 86
  20. 26
  21. 73
  22. 24
  23. 52
  24. 4
  25. 57
  26. 77
  27. 84
  28. 74
  29. 6
  30. 30
  31. 565
  32. 72
  33. 25
  34. 799
  35. 68
  36. 295
  37. 68
  38. 683
  39. 55
  40. 67

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