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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 434 · 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. 1.68 + 19 =
  2. 2.220 − 99 =
  3. 3.66 + 9 =
  4. 4.580 − 99 =
  5. 5.20 − 9 =
  6. 6.25 − 19 =
  7. 7.34 − 29 =
  8. 8.13 + 19 =
  9. 9.14 − 9 =
  10. 10.84 − 29 =
  11. 11.82 − 29 =
  12. 12.158 + 99 =
  13. 13.12 − 9 =
  14. 14.76 − 19 =
  15. 15.44 − 19 =
  16. 16.36 − 29 =
  17. 17.69 − 19 =
  18. 18.378 − 99 =
  19. 19.238 − 99 =
  20. 20.64 + 9 =
  21. 21.90 − 19 =
  22. 22.77 − 19 =
  23. 23.31 + 29 =
  24. 24.477 − 99 =
  25. 25.799 − 99 =
  26. 26.40 + 9 =
  27. 27.697 − 99 =
  28. 28.51 − 9 =
  29. 29.49 + 29 =
  30. 30.56 + 9 =
  31. 31.69 + 19 =
  32. 32.86 − 19 =
  33. 33.67 + 9 =
  34. 34.71 + 29 =
  35. 35.107 − 29 =
  36. 36.421 + 99 =
  37. 37.66 − 29 =
  38. 38.28 + 19 =
  39. 39.209 − 99 =
  40. 40.584 − 99 =

Answer key

  1. 87
  2. 121
  3. 75
  4. 481
  5. 11
  6. 6
  7. 5
  8. 32
  9. 5
  10. 55
  11. 53
  12. 257
  13. 3
  14. 57
  15. 25
  16. 7
  17. 50
  18. 279
  19. 139
  20. 73
  21. 71
  22. 58
  23. 60
  24. 378
  25. 700
  26. 49
  27. 598
  28. 42
  29. 78
  30. 65
  31. 88
  32. 67
  33. 76
  34. 100
  35. 78
  36. 520
  37. 37
  38. 47
  39. 110
  40. 485

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