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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 608 · 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. 1.58 − 29 =
  2. 2.109 − 29 =
  3. 3.53 − 19 =
  4. 4.58 + 19 =
  5. 5.24 + 19 =
  6. 6.59 + 19 =
  7. 7.15 + 9 =
  8. 8.487 + 99 =
  9. 9.52 + 9 =
  10. 10.785 + 99 =
  11. 11.519 + 99 =
  12. 12.74 + 19 =
  13. 13.48 − 19 =
  14. 14.56 − 29 =
  15. 15.737 − 99 =
  16. 16.38 − 29 =
  17. 17.41 − 19 =
  18. 18.63 − 29 =
  19. 19.49 + 29 =
  20. 20.391 − 99 =
  21. 21.591 − 99 =
  22. 22.72 + 19 =
  23. 23.201 + 99 =
  24. 24.32 + 29 =
  25. 25.155 − 99 =
  26. 26.37 − 9 =
  27. 27.68 + 29 =
  28. 28.69 − 9 =
  29. 29.24 − 9 =
  30. 30.403 − 99 =
  31. 31.67 − 29 =
  32. 32.74 − 19 =
  33. 33.644 + 99 =
  34. 34.43 + 9 =
  35. 35.51 + 9 =
  36. 36.49 − 29 =
  37. 37.596 + 99 =
  38. 38.41 + 9 =
  39. 39.70 + 9 =
  40. 40.52 − 29 =

Answer key

  1. 29
  2. 80
  3. 34
  4. 77
  5. 43
  6. 78
  7. 24
  8. 586
  9. 61
  10. 884
  11. 618
  12. 93
  13. 29
  14. 27
  15. 638
  16. 9
  17. 22
  18. 34
  19. 78
  20. 292
  21. 492
  22. 91
  23. 300
  24. 61
  25. 56
  26. 28
  27. 97
  28. 60
  29. 15
  30. 304
  31. 38
  32. 55
  33. 743
  34. 52
  35. 60
  36. 20
  37. 695
  38. 50
  39. 79
  40. 23

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