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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 126 · 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. 1.73 − 9 =
  2. 2.64 + 9 =
  3. 3.65 − 29 =
  4. 4.474 + 99 =
  5. 5.64 + 29 =
  6. 6.513 + 99 =
  7. 7.580 + 99 =
  8. 8.24 + 9 =
  9. 9.380 + 99 =
  10. 10.73 + 29 =
  11. 11.277 − 99 =
  12. 12.787 − 99 =
  13. 13.152 − 99 =
  14. 14.847 − 99 =
  15. 15.40 + 9 =
  16. 16.50 + 29 =
  17. 17.18 + 19 =
  18. 18.61 + 19 =
  19. 19.33 − 9 =
  20. 20.58 − 29 =
  21. 21.52 − 9 =
  22. 22.58 − 19 =
  23. 23.43 − 19 =
  24. 24.76 + 29 =
  25. 25.54 + 9 =
  26. 26.768 − 99 =
  27. 27.55 − 9 =
  28. 28.687 − 99 =
  29. 29.213 + 99 =
  30. 30.66 − 29 =
  31. 31.109 − 29 =
  32. 32.34 − 29 =
  33. 33.97 − 29 =
  34. 34.63 − 9 =
  35. 35.71 + 29 =
  36. 36.53 − 9 =
  37. 37.50 + 9 =
  38. 38.51 − 19 =
  39. 39.26 + 29 =
  40. 40.38 − 29 =

Answer key

  1. 64
  2. 73
  3. 36
  4. 573
  5. 93
  6. 612
  7. 679
  8. 33
  9. 479
  10. 102
  11. 178
  12. 688
  13. 53
  14. 748
  15. 49
  16. 79
  17. 37
  18. 80
  19. 24
  20. 29
  21. 43
  22. 39
  23. 24
  24. 105
  25. 63
  26. 669
  27. 46
  28. 588
  29. 312
  30. 37
  31. 80
  32. 5
  33. 68
  34. 54
  35. 100
  36. 44
  37. 59
  38. 32
  39. 55
  40. 9

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