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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 321 · 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. 1.22 − 19 =
  2. 2.78 − 9 =
  3. 3.394 + 99 =
  4. 4.42 − 29 =
  5. 5.43 − 9 =
  6. 6.51 − 9 =
  7. 7.78 − 29 =
  8. 8.14 + 29 =
  9. 9.59 + 29 =
  10. 10.44 + 29 =
  11. 11.231 + 99 =
  12. 12.18 + 9 =
  13. 13.45 − 29 =
  14. 14.47 + 19 =
  15. 15.758 + 99 =
  16. 16.26 + 9 =
  17. 17.21 + 9 =
  18. 18.62 − 29 =
  19. 19.68 − 29 =
  20. 20.243 − 99 =
  21. 21.67 + 9 =
  22. 22.28 − 9 =
  23. 23.22 + 9 =
  24. 24.108 − 29 =
  25. 25.83 − 9 =
  26. 26.88 − 9 =
  27. 27.48 + 9 =
  28. 28.52 + 9 =
  29. 29.45 + 9 =
  30. 30.72 − 19 =
  31. 31.227 − 99 =
  32. 32.387 + 99 =
  33. 33.213 − 99 =
  34. 34.62 − 9 =
  35. 35.26 + 29 =
  36. 36.99 − 19 =
  37. 37.69 − 9 =
  38. 38.34 + 29 =
  39. 39.72 − 9 =
  40. 40.69 − 29 =

Answer key

  1. 3
  2. 69
  3. 493
  4. 13
  5. 34
  6. 42
  7. 49
  8. 43
  9. 88
  10. 73
  11. 330
  12. 27
  13. 16
  14. 66
  15. 857
  16. 35
  17. 30
  18. 33
  19. 39
  20. 144
  21. 76
  22. 19
  23. 31
  24. 79
  25. 74
  26. 79
  27. 57
  28. 61
  29. 54
  30. 53
  31. 128
  32. 486
  33. 114
  34. 53
  35. 55
  36. 80
  37. 60
  38. 63
  39. 63
  40. 40

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