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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 478 · 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. 1.20 + 19 =
  2. 2.23 − 9 =
  3. 3.19 + 19 =
  4. 4.41 − 29 =
  5. 5.230 − 99 =
  6. 6.404 + 99 =
  7. 7.64 − 19 =
  8. 8.280 + 99 =
  9. 9.39 − 9 =
  10. 10.17 − 9 =
  11. 11.357 − 99 =
  12. 12.71 − 29 =
  13. 13.24 + 9 =
  14. 14.29 + 9 =
  15. 15.85 − 29 =
  16. 16.65 + 19 =
  17. 17.45 − 29 =
  18. 18.42 + 29 =
  19. 19.447 + 99 =
  20. 20.104 − 29 =
  21. 21.14 − 9 =
  22. 22.46 − 19 =
  23. 23.60 − 9 =
  24. 24.101 − 29 =
  25. 25.785 + 99 =
  26. 26.71 + 9 =
  27. 27.15 + 9 =
  28. 28.18 + 9 =
  29. 29.29 + 29 =
  30. 30.609 − 99 =
  31. 31.63 − 29 =
  32. 32.22 + 19 =
  33. 33.497 + 99 =
  34. 34.56 − 29 =
  35. 35.85 − 9 =
  36. 36.163 + 99 =
  37. 37.193 − 99 =
  38. 38.486 + 99 =
  39. 39.98 − 19 =
  40. 40.108 − 29 =

Answer key

  1. 39
  2. 14
  3. 38
  4. 12
  5. 131
  6. 503
  7. 45
  8. 379
  9. 30
  10. 8
  11. 258
  12. 42
  13. 33
  14. 38
  15. 56
  16. 84
  17. 16
  18. 71
  19. 546
  20. 75
  21. 5
  22. 27
  23. 51
  24. 72
  25. 884
  26. 80
  27. 24
  28. 27
  29. 58
  30. 510
  31. 34
  32. 41
  33. 596
  34. 27
  35. 76
  36. 262
  37. 94
  38. 585
  39. 79
  40. 79

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