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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 397 · 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. 1.499 + 99 =
  2. 2.59 + 9 =
  3. 3.74 + 9 =
  4. 4.52 − 19 =
  5. 5.78 + 19 =
  6. 6.256 − 99 =
  7. 7.98 − 29 =
  8. 8.72 − 29 =
  9. 9.37 + 29 =
  10. 10.69 − 19 =
  11. 11.811 − 99 =
  12. 12.22 + 9 =
  13. 13.76 − 9 =
  14. 14.72 + 19 =
  15. 15.164 − 99 =
  16. 16.76 + 19 =
  17. 17.69 − 29 =
  18. 18.575 − 99 =
  19. 19.88 − 9 =
  20. 20.54 − 9 =
  21. 21.77 + 29 =
  22. 22.76 − 19 =
  23. 23.583 + 99 =
  24. 24.65 + 29 =
  25. 25.72 + 9 =
  26. 26.17 + 29 =
  27. 27.54 − 29 =
  28. 28.96 − 29 =
  29. 29.73 + 9 =
  30. 30.57 + 9 =
  31. 31.108 − 29 =
  32. 32.74 + 29 =
  33. 33.38 + 9 =
  34. 34.809 − 99 =
  35. 35.91 − 19 =
  36. 36.33 + 19 =
  37. 37.35 + 19 =
  38. 38.89 − 29 =
  39. 39.80 + 9 =
  40. 40.61 − 19 =

Answer key

  1. 598
  2. 68
  3. 83
  4. 33
  5. 97
  6. 157
  7. 69
  8. 43
  9. 66
  10. 50
  11. 712
  12. 31
  13. 67
  14. 91
  15. 65
  16. 95
  17. 40
  18. 476
  19. 79
  20. 45
  21. 106
  22. 57
  23. 682
  24. 94
  25. 81
  26. 46
  27. 25
  28. 67
  29. 82
  30. 66
  31. 79
  32. 103
  33. 47
  34. 710
  35. 72
  36. 52
  37. 54
  38. 60
  39. 89
  40. 42

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