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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 934 · 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. 1.101 − 29 =
  2. 2.45 − 9 =
  3. 3.59 + 29 =
  4. 4.663 − 99 =
  5. 5.72 + 19 =
  6. 6.30 + 9 =
  7. 7.59 + 19 =
  8. 8.36 + 9 =
  9. 9.16 − 9 =
  10. 10.71 + 29 =
  11. 11.45 + 9 =
  12. 12.63 − 19 =
  13. 13.24 + 9 =
  14. 14.42 + 9 =
  15. 15.14 − 9 =
  16. 16.283 − 99 =
  17. 17.13 + 29 =
  18. 18.21 + 9 =
  19. 19.589 + 99 =
  20. 20.465 − 99 =
  21. 21.18 + 9 =
  22. 22.54 − 29 =
  23. 23.44 − 9 =
  24. 24.80 + 19 =
  25. 25.32 − 19 =
  26. 26.348 + 99 =
  27. 27.19 + 9 =
  28. 28.52 + 19 =
  29. 29.65 − 9 =
  30. 30.95 − 19 =
  31. 31.58 − 19 =
  32. 32.17 + 9 =
  33. 33.33 + 29 =
  34. 34.86 − 19 =
  35. 35.85 − 9 =
  36. 36.13 + 19 =
  37. 37.46 + 9 =
  38. 38.91 − 29 =
  39. 39.77 + 9 =
  40. 40.12 + 19 =

Answer key

  1. 72
  2. 36
  3. 88
  4. 564
  5. 91
  6. 39
  7. 78
  8. 45
  9. 7
  10. 100
  11. 54
  12. 44
  13. 33
  14. 51
  15. 5
  16. 184
  17. 42
  18. 30
  19. 688
  20. 366
  21. 27
  22. 25
  23. 35
  24. 99
  25. 13
  26. 447
  27. 28
  28. 71
  29. 56
  30. 76
  31. 39
  32. 26
  33. 62
  34. 67
  35. 76
  36. 32
  37. 55
  38. 62
  39. 86
  40. 31

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