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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 507 · 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. 1.48 − 9 =
  2. 2.75 − 19 =
  3. 3.48 + 9 =
  4. 4.508 + 99 =
  5. 5.16 + 19 =
  6. 6.87 − 19 =
  7. 7.685 + 99 =
  8. 8.517 + 99 =
  9. 9.78 + 19 =
  10. 10.209 − 99 =
  11. 11.503 + 99 =
  12. 12.29 + 29 =
  13. 13.35 − 19 =
  14. 14.251 + 99 =
  15. 15.52 + 9 =
  16. 16.46 + 19 =
  17. 17.457 − 99 =
  18. 18.193 + 99 =
  19. 19.623 + 99 =
  20. 20.45 + 9 =
  21. 21.49 − 9 =
  22. 22.882 − 99 =
  23. 23.59 + 9 =
  24. 24.88 − 9 =
  25. 25.12 + 29 =
  26. 26.564 + 99 =
  27. 27.75 + 29 =
  28. 28.76 − 9 =
  29. 29.27 + 9 =
  30. 30.74 + 9 =
  31. 31.29 + 9 =
  32. 32.72 + 29 =
  33. 33.14 − 9 =
  34. 34.47 + 9 =
  35. 35.43 + 19 =
  36. 36.74 + 29 =
  37. 37.46 − 9 =
  38. 38.455 − 99 =
  39. 39.35 + 9 =
  40. 40.63 − 9 =

Answer key

  1. 39
  2. 56
  3. 57
  4. 607
  5. 35
  6. 68
  7. 784
  8. 616
  9. 97
  10. 110
  11. 602
  12. 58
  13. 16
  14. 350
  15. 61
  16. 65
  17. 358
  18. 292
  19. 722
  20. 54
  21. 40
  22. 783
  23. 68
  24. 79
  25. 41
  26. 663
  27. 104
  28. 67
  29. 36
  30. 83
  31. 38
  32. 101
  33. 5
  34. 56
  35. 62
  36. 103
  37. 37
  38. 356
  39. 44
  40. 54

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