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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 957 · 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 − 9 =
  2. 2.77 − 19 =
  3. 3.20 + 29 =
  4. 4.16 − 9 =
  5. 5.563 + 99 =
  6. 6.14 − 9 =
  7. 7.39 + 9 =
  8. 8.58 + 19 =
  9. 9.23 + 9 =
  10. 10.37 − 9 =
  11. 11.53 − 29 =
  12. 12.23 + 29 =
  13. 13.84 − 9 =
  14. 14.47 − 19 =
  15. 15.29 + 19 =
  16. 16.36 + 9 =
  17. 17.53 + 29 =
  18. 18.761 − 99 =
  19. 19.61 − 9 =
  20. 20.60 + 19 =
  21. 21.74 + 19 =
  22. 22.67 + 9 =
  23. 23.67 − 19 =
  24. 24.94 − 19 =
  25. 25.506 + 99 =
  26. 26.740 − 99 =
  27. 27.88 − 19 =
  28. 28.75 − 29 =
  29. 29.171 − 99 =
  30. 30.104 − 29 =
  31. 31.633 − 99 =
  32. 32.781 + 99 =
  33. 33.21 + 29 =
  34. 34.72 + 9 =
  35. 35.66 + 9 =
  36. 36.70 − 19 =
  37. 37.390 + 99 =
  38. 38.36 − 19 =
  39. 39.72 − 9 =
  40. 40.53 + 9 =

Answer key

  1. 25
  2. 58
  3. 49
  4. 7
  5. 662
  6. 5
  7. 48
  8. 77
  9. 32
  10. 28
  11. 24
  12. 52
  13. 75
  14. 28
  15. 48
  16. 45
  17. 82
  18. 662
  19. 52
  20. 79
  21. 93
  22. 76
  23. 48
  24. 75
  25. 605
  26. 641
  27. 69
  28. 46
  29. 72
  30. 75
  31. 534
  32. 880
  33. 50
  34. 81
  35. 75
  36. 51
  37. 489
  38. 17
  39. 63
  40. 62

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