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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 105 · 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. 1.32 − 29 =
  2. 2.80 − 9 =
  3. 3.625 + 99 =
  4. 4.78 + 29 =
  5. 5.43 + 19 =
  6. 6.16 + 9 =
  7. 7.265 + 99 =
  8. 8.80 − 19 =
  9. 9.58 + 29 =
  10. 10.86 − 19 =
  11. 11.31 − 19 =
  12. 12.44 + 29 =
  13. 13.297 + 99 =
  14. 14.39 + 9 =
  15. 15.16 + 19 =
  16. 16.76 + 19 =
  17. 17.66 + 29 =
  18. 18.687 + 99 =
  19. 19.30 + 19 =
  20. 20.408 − 99 =
  21. 21.33 + 19 =
  22. 22.76 + 9 =
  23. 23.112 + 99 =
  24. 24.736 + 99 =
  25. 25.25 + 29 =
  26. 26.73 + 19 =
  27. 27.41 − 29 =
  28. 28.87 − 9 =
  29. 29.66 − 19 =
  30. 30.48 − 19 =
  31. 31.384 − 99 =
  32. 32.559 + 99 =
  33. 33.33 − 29 =
  34. 34.13 + 9 =
  35. 35.97 − 19 =
  36. 36.31 + 9 =
  37. 37.77 + 29 =
  38. 38.37 + 9 =
  39. 39.72 − 9 =
  40. 40.27 + 9 =

Answer key

  1. 3
  2. 71
  3. 724
  4. 107
  5. 62
  6. 25
  7. 364
  8. 61
  9. 87
  10. 67
  11. 12
  12. 73
  13. 396
  14. 48
  15. 35
  16. 95
  17. 95
  18. 786
  19. 49
  20. 309
  21. 52
  22. 85
  23. 211
  24. 835
  25. 54
  26. 92
  27. 12
  28. 78
  29. 47
  30. 29
  31. 285
  32. 658
  33. 4
  34. 22
  35. 78
  36. 40
  37. 106
  38. 46
  39. 63
  40. 36

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