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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 352 · 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 + 9 =
  2. 2.124 + 99 =
  3. 3.48 − 9 =
  4. 4.66 + 19 =
  5. 5.50 + 29 =
  6. 6.25 + 29 =
  7. 7.55 − 29 =
  8. 8.107 + 99 =
  9. 9.38 + 29 =
  10. 10.39 − 19 =
  11. 11.211 + 99 =
  12. 12.49 + 9 =
  13. 13.324 + 99 =
  14. 14.62 − 19 =
  15. 15.79 + 9 =
  16. 16.15 + 29 =
  17. 17.57 + 29 =
  18. 18.73 + 19 =
  19. 19.539 − 99 =
  20. 20.558 + 99 =
  21. 21.40 − 29 =
  22. 22.29 + 19 =
  23. 23.28 + 19 =
  24. 24.24 + 19 =
  25. 25.771 − 99 =
  26. 26.20 + 19 =
  27. 27.48 + 9 =
  28. 28.303 + 99 =
  29. 29.425 − 99 =
  30. 30.31 + 9 =
  31. 31.33 − 9 =
  32. 32.76 + 19 =
  33. 33.37 − 9 =
  34. 34.122 + 99 =
  35. 35.714 + 99 =
  36. 36.41 + 9 =
  37. 37.18 + 9 =
  38. 38.59 + 9 =
  39. 39.78 + 9 =
  40. 40.80 − 29 =

Answer key

  1. 41
  2. 223
  3. 39
  4. 85
  5. 79
  6. 54
  7. 26
  8. 206
  9. 67
  10. 20
  11. 310
  12. 58
  13. 423
  14. 43
  15. 88
  16. 44
  17. 86
  18. 92
  19. 440
  20. 657
  21. 11
  22. 48
  23. 47
  24. 43
  25. 672
  26. 39
  27. 57
  28. 402
  29. 326
  30. 40
  31. 24
  32. 95
  33. 28
  34. 221
  35. 813
  36. 50
  37. 27
  38. 68
  39. 87
  40. 51

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