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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 520 · 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. 2.37 − 29 =
  3. 3.681 + 99 =
  4. 4.88 − 19 =
  5. 5.30 − 19 =
  6. 6.25 + 9 =
  7. 7.36 − 19 =
  8. 8.46 + 19 =
  9. 9.52 − 29 =
  10. 10.79 + 9 =
  11. 11.71 − 19 =
  12. 12.279 − 99 =
  13. 13.14 + 9 =
  14. 14.31 + 29 =
  15. 15.685 + 99 =
  16. 16.50 + 9 =
  17. 17.185 + 99 =
  18. 18.13 + 29 =
  19. 19.69 − 9 =
  20. 20.711 + 99 =
  21. 21.63 + 9 =
  22. 22.56 − 29 =
  23. 23.236 + 99 =
  24. 24.388 + 99 =
  25. 25.768 + 99 =
  26. 26.61 + 9 =
  27. 27.333 + 99 =
  28. 28.76 + 19 =
  29. 29.67 + 19 =
  30. 30.40 − 19 =
  31. 31.23 − 19 =
  32. 32.23 + 29 =
  33. 33.72 − 19 =
  34. 34.70 + 19 =
  35. 35.829 − 99 =
  36. 36.45 + 19 =
  37. 37.16 + 29 =
  38. 38.71 − 29 =
  39. 39.107 + 99 =
  40. 40.50 − 29 =

Answer key

  1. 23
  2. 8
  3. 780
  4. 69
  5. 11
  6. 34
  7. 17
  8. 65
  9. 23
  10. 88
  11. 52
  12. 180
  13. 23
  14. 60
  15. 784
  16. 59
  17. 284
  18. 42
  19. 60
  20. 810
  21. 72
  22. 27
  23. 335
  24. 487
  25. 867
  26. 70
  27. 432
  28. 95
  29. 86
  30. 21
  31. 4
  32. 52
  33. 53
  34. 89
  35. 730
  36. 64
  37. 45
  38. 42
  39. 206
  40. 21

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