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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 988 · 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. 1.569 − 99 =
  2. 2.14 + 19 =
  3. 3.70 + 9 =
  4. 4.64 − 19 =
  5. 5.71 + 19 =
  6. 6.73 + 29 =
  7. 7.59 − 19 =
  8. 8.857 − 99 =
  9. 9.64 + 9 =
  10. 10.86 − 9 =
  11. 11.17 + 9 =
  12. 12.17 − 9 =
  13. 13.38 + 9 =
  14. 14.80 − 29 =
  15. 15.29 + 19 =
  16. 16.29 + 9 =
  17. 17.43 − 9 =
  18. 18.340 − 99 =
  19. 19.746 − 99 =
  20. 20.64 − 9 =
  21. 21.41 + 9 =
  22. 22.63 − 29 =
  23. 23.76 − 19 =
  24. 24.46 − 19 =
  25. 25.53 + 9 =
  26. 26.38 − 29 =
  27. 27.47 + 29 =
  28. 28.30 + 9 =
  29. 29.48 − 29 =
  30. 30.20 + 29 =
  31. 31.592 − 99 =
  32. 32.71 + 9 =
  33. 33.48 − 9 =
  34. 34.19 + 9 =
  35. 35.43 − 29 =
  36. 36.29 − 19 =
  37. 37.99 − 29 =
  38. 38.51 − 29 =
  39. 39.162 − 99 =
  40. 40.54 + 29 =

Answer key

  1. 470
  2. 33
  3. 79
  4. 45
  5. 90
  6. 102
  7. 40
  8. 758
  9. 73
  10. 77
  11. 26
  12. 8
  13. 47
  14. 51
  15. 48
  16. 38
  17. 34
  18. 241
  19. 647
  20. 55
  21. 50
  22. 34
  23. 57
  24. 27
  25. 62
  26. 9
  27. 76
  28. 39
  29. 19
  30. 49
  31. 493
  32. 80
  33. 39
  34. 28
  35. 14
  36. 10
  37. 70
  38. 22
  39. 63
  40. 83

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