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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 883 · 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. 1.45 + 29 =
  2. 2.22 + 29 =
  3. 3.61 + 29 =
  4. 4.304 + 99 =
  5. 5.16 + 29 =
  6. 6.123 + 99 =
  7. 7.20 + 9 =
  8. 8.56 + 9 =
  9. 9.22 − 19 =
  10. 10.65 − 9 =
  11. 11.17 + 9 =
  12. 12.221 − 99 =
  13. 13.54 − 9 =
  14. 14.305 + 99 =
  15. 15.57 + 9 =
  16. 16.549 + 99 =
  17. 17.36 − 19 =
  18. 18.39 + 9 =
  19. 19.71 − 19 =
  20. 20.36 + 9 =
  21. 21.93 − 29 =
  22. 22.69 + 9 =
  23. 23.15 + 29 =
  24. 24.41 − 9 =
  25. 25.46 + 19 =
  26. 26.34 + 9 =
  27. 27.19 − 9 =
  28. 28.25 − 9 =
  29. 29.581 + 99 =
  30. 30.81 − 19 =
  31. 31.120 + 99 =
  32. 32.624 + 99 =
  33. 33.33 − 19 =
  34. 34.76 + 9 =
  35. 35.56 + 19 =
  36. 36.58 − 19 =
  37. 37.465 + 99 =
  38. 38.34 − 19 =
  39. 39.319 − 99 =
  40. 40.39 − 29 =

Answer key

  1. 74
  2. 51
  3. 90
  4. 403
  5. 45
  6. 222
  7. 29
  8. 65
  9. 3
  10. 56
  11. 26
  12. 122
  13. 45
  14. 404
  15. 66
  16. 648
  17. 17
  18. 48
  19. 52
  20. 45
  21. 64
  22. 78
  23. 44
  24. 32
  25. 65
  26. 43
  27. 10
  28. 16
  29. 680
  30. 62
  31. 219
  32. 723
  33. 14
  34. 85
  35. 75
  36. 39
  37. 564
  38. 15
  39. 220
  40. 10

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