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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 580 · 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. 1.34 − 29 =
  2. 2.65 − 19 =
  3. 3.72 − 19 =
  4. 4.37 + 29 =
  5. 5.78 + 19 =
  6. 6.447 − 99 =
  7. 7.64 − 29 =
  8. 8.23 − 9 =
  9. 9.57 − 9 =
  10. 10.63 − 19 =
  11. 11.478 + 99 =
  12. 12.34 + 19 =
  13. 13.32 + 9 =
  14. 14.551 + 99 =
  15. 15.860 − 99 =
  16. 16.64 + 9 =
  17. 17.78 − 19 =
  18. 18.331 − 99 =
  19. 19.56 − 9 =
  20. 20.32 + 19 =
  21. 21.29 − 9 =
  22. 22.41 + 19 =
  23. 23.53 − 9 =
  24. 24.45 + 19 =
  25. 25.74 − 29 =
  26. 26.322 − 99 =
  27. 27.56 + 29 =
  28. 28.69 + 19 =
  29. 29.621 − 99 =
  30. 30.56 + 19 =
  31. 31.24 − 9 =
  32. 32.71 − 29 =
  33. 33.67 − 19 =
  34. 34.75 + 9 =
  35. 35.23 + 9 =
  36. 36.74 + 9 =
  37. 37.12 − 9 =
  38. 38.32 + 29 =
  39. 39.787 + 99 =
  40. 40.17 − 9 =

Answer key

  1. 5
  2. 46
  3. 53
  4. 66
  5. 97
  6. 348
  7. 35
  8. 14
  9. 48
  10. 44
  11. 577
  12. 53
  13. 41
  14. 650
  15. 761
  16. 73
  17. 59
  18. 232
  19. 47
  20. 51
  21. 20
  22. 60
  23. 44
  24. 64
  25. 45
  26. 223
  27. 85
  28. 88
  29. 522
  30. 75
  31. 15
  32. 42
  33. 48
  34. 84
  35. 32
  36. 83
  37. 3
  38. 61
  39. 886
  40. 8

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