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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 822 · 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. 1.248 − 99 =
  2. 2.26 − 9 =
  3. 3.51 + 19 =
  4. 4.19 + 29 =
  5. 5.39 + 29 =
  6. 6.380 − 99 =
  7. 7.34 − 9 =
  8. 8.62 + 19 =
  9. 9.58 − 29 =
  10. 10.44 + 29 =
  11. 11.67 − 9 =
  12. 12.305 + 99 =
  13. 13.97 − 29 =
  14. 14.43 − 19 =
  15. 15.76 − 19 =
  16. 16.629 − 99 =
  17. 17.71 − 9 =
  18. 18.15 + 9 =
  19. 19.73 − 19 =
  20. 20.471 + 99 =
  21. 21.684 + 99 =
  22. 22.56 + 29 =
  23. 23.61 + 19 =
  24. 24.36 − 19 =
  25. 25.56 + 9 =
  26. 26.80 − 9 =
  27. 27.53 + 9 =
  28. 28.12 + 29 =
  29. 29.798 − 99 =
  30. 30.22 − 19 =
  31. 31.498 + 99 =
  32. 32.74 + 19 =
  33. 33.591 + 99 =
  34. 34.597 + 99 =
  35. 35.72 + 9 =
  36. 36.64 + 9 =
  37. 37.21 + 19 =
  38. 38.38 − 19 =
  39. 39.483 + 99 =
  40. 40.46 − 29 =

Answer key

  1. 149
  2. 17
  3. 70
  4. 48
  5. 68
  6. 281
  7. 25
  8. 81
  9. 29
  10. 73
  11. 58
  12. 404
  13. 68
  14. 24
  15. 57
  16. 530
  17. 62
  18. 24
  19. 54
  20. 570
  21. 783
  22. 85
  23. 80
  24. 17
  25. 65
  26. 71
  27. 62
  28. 41
  29. 699
  30. 3
  31. 597
  32. 93
  33. 690
  34. 696
  35. 81
  36. 73
  37. 40
  38. 19
  39. 582
  40. 17

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