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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 951 · 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. 1.28 + 19 =
  2. 2.355 + 99 =
  3. 3.13 − 9 =
  4. 4.34 + 9 =
  5. 5.34 − 19 =
  6. 6.80 + 9 =
  7. 7.23 + 19 =
  8. 8.20 + 29 =
  9. 9.16 + 29 =
  10. 10.75 + 19 =
  11. 11.51 − 19 =
  12. 12.43 + 9 =
  13. 13.27 + 9 =
  14. 14.18 − 9 =
  15. 15.45 − 19 =
  16. 16.38 + 9 =
  17. 17.26 + 19 =
  18. 18.43 + 29 =
  19. 19.185 − 99 =
  20. 20.49 + 29 =
  21. 21.48 − 29 =
  22. 22.403 + 99 =
  23. 23.88 − 9 =
  24. 24.50 + 9 =
  25. 25.177 − 99 =
  26. 26.35 + 9 =
  27. 27.739 + 99 =
  28. 28.27 + 29 =
  29. 29.117 + 99 =
  30. 30.66 + 9 =
  31. 31.45 + 29 =
  32. 32.375 − 99 =
  33. 33.28 − 19 =
  34. 34.54 − 29 =
  35. 35.51 + 29 =
  36. 36.64 + 29 =
  37. 37.114 + 99 =
  38. 38.53 + 29 =
  39. 39.89 − 9 =
  40. 40.29 + 19 =

Answer key

  1. 47
  2. 454
  3. 4
  4. 43
  5. 15
  6. 89
  7. 42
  8. 49
  9. 45
  10. 94
  11. 32
  12. 52
  13. 36
  14. 9
  15. 26
  16. 47
  17. 45
  18. 72
  19. 86
  20. 78
  21. 19
  22. 502
  23. 79
  24. 59
  25. 78
  26. 44
  27. 838
  28. 56
  29. 216
  30. 75
  31. 74
  32. 276
  33. 9
  34. 25
  35. 80
  36. 93
  37. 213
  38. 82
  39. 80
  40. 48

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