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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 195 · 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. 1.12 − 9 =
  2. 2.34 + 9 =
  3. 3.629 + 99 =
  4. 4.33 + 9 =
  5. 5.35 + 9 =
  6. 6.30 − 9 =
  7. 7.51 + 19 =
  8. 8.83 − 9 =
  9. 9.462 − 99 =
  10. 10.70 − 19 =
  11. 11.61 − 9 =
  12. 12.59 + 29 =
  13. 13.52 + 29 =
  14. 14.151 − 99 =
  15. 15.795 − 99 =
  16. 16.21 + 19 =
  17. 17.33 − 29 =
  18. 18.31 + 29 =
  19. 19.34 − 9 =
  20. 20.747 + 99 =
  21. 21.510 + 99 =
  22. 22.70 + 9 =
  23. 23.78 + 9 =
  24. 24.49 − 9 =
  25. 25.59 + 9 =
  26. 26.52 − 29 =
  27. 27.522 + 99 =
  28. 28.63 − 19 =
  29. 29.22 + 9 =
  30. 30.60 − 29 =
  31. 31.386 + 99 =
  32. 32.14 + 9 =
  33. 33.27 + 9 =
  34. 34.46 + 9 =
  35. 35.287 + 99 =
  36. 36.17 − 9 =
  37. 37.86 − 19 =
  38. 38.77 + 29 =
  39. 39.19 + 9 =
  40. 40.68 + 19 =

Answer key

  1. 3
  2. 43
  3. 728
  4. 42
  5. 44
  6. 21
  7. 70
  8. 74
  9. 363
  10. 51
  11. 52
  12. 88
  13. 81
  14. 52
  15. 696
  16. 40
  17. 4
  18. 60
  19. 25
  20. 846
  21. 609
  22. 79
  23. 87
  24. 40
  25. 68
  26. 23
  27. 621
  28. 44
  29. 31
  30. 31
  31. 485
  32. 23
  33. 36
  34. 55
  35. 386
  36. 8
  37. 67
  38. 106
  39. 28
  40. 87

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