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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 130 · 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. 1.72 + 29 =
  2. 2.58 + 19 =
  3. 3.780 − 99 =
  4. 4.78 − 29 =
  5. 5.52 + 19 =
  6. 6.54 − 29 =
  7. 7.720 − 99 =
  8. 8.74 + 9 =
  9. 9.14 + 19 =
  10. 10.37 − 9 =
  11. 11.59 + 19 =
  12. 12.63 − 9 =
  13. 13.259 + 99 =
  14. 14.28 − 19 =
  15. 15.21 − 9 =
  16. 16.70 − 19 =
  17. 17.221 − 99 =
  18. 18.48 − 19 =
  19. 19.494 − 99 =
  20. 20.47 + 19 =
  21. 21.81 − 29 =
  22. 22.26 − 9 =
  23. 23.600 + 99 =
  24. 24.54 − 9 =
  25. 25.83 − 19 =
  26. 26.50 − 9 =
  27. 27.29 − 9 =
  28. 28.72 − 19 =
  29. 29.69 − 9 =
  30. 30.34 − 19 =
  31. 31.36 + 29 =
  32. 32.33 − 9 =
  33. 33.43 + 19 =
  34. 34.893 − 99 =
  35. 35.55 + 29 =
  36. 36.290 + 99 =
  37. 37.87 − 19 =
  38. 38.30 + 9 =
  39. 39.29 + 19 =
  40. 40.495 + 99 =

Answer key

  1. 101
  2. 77
  3. 681
  4. 49
  5. 71
  6. 25
  7. 621
  8. 83
  9. 33
  10. 28
  11. 78
  12. 54
  13. 358
  14. 9
  15. 12
  16. 51
  17. 122
  18. 29
  19. 395
  20. 66
  21. 52
  22. 17
  23. 699
  24. 45
  25. 64
  26. 41
  27. 20
  28. 53
  29. 60
  30. 15
  31. 65
  32. 24
  33. 62
  34. 794
  35. 84
  36. 389
  37. 68
  38. 39
  39. 48
  40. 594

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