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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 995 · 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. 1.137 + 99 =
  2. 2.42 + 19 =
  3. 3.444 − 99 =
  4. 4.41 + 19 =
  5. 5.74 + 9 =
  6. 6.79 − 9 =
  7. 7.548 + 99 =
  8. 8.33 − 29 =
  9. 9.28 + 9 =
  10. 10.52 + 19 =
  11. 11.55 − 29 =
  12. 12.640 + 99 =
  13. 13.486 − 99 =
  14. 14.27 + 29 =
  15. 15.56 + 9 =
  16. 16.71 + 9 =
  17. 17.17 − 9 =
  18. 18.87 − 19 =
  19. 19.220 + 99 =
  20. 20.55 + 9 =
  21. 21.234 − 99 =
  22. 22.48 + 29 =
  23. 23.35 + 29 =
  24. 24.761 + 99 =
  25. 25.14 − 9 =
  26. 26.22 + 19 =
  27. 27.665 + 99 =
  28. 28.59 + 29 =
  29. 29.65 − 29 =
  30. 30.67 + 19 =
  31. 31.12 + 29 =
  32. 32.17 + 9 =
  33. 33.61 + 19 =
  34. 34.36 − 9 =
  35. 35.63 + 9 =
  36. 36.210 − 99 =
  37. 37.51 − 19 =
  38. 38.37 + 9 =
  39. 39.37 + 19 =
  40. 40.73 + 29 =

Answer key

  1. 236
  2. 61
  3. 345
  4. 60
  5. 83
  6. 70
  7. 647
  8. 4
  9. 37
  10. 71
  11. 26
  12. 739
  13. 387
  14. 56
  15. 65
  16. 80
  17. 8
  18. 68
  19. 319
  20. 64
  21. 135
  22. 77
  23. 64
  24. 860
  25. 5
  26. 41
  27. 764
  28. 88
  29. 36
  30. 86
  31. 41
  32. 26
  33. 80
  34. 27
  35. 72
  36. 111
  37. 32
  38. 46
  39. 56
  40. 102

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