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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 638 · 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. 1.31 − 19 =
  2. 2.612 + 99 =
  3. 3.32 + 9 =
  4. 4.325 + 99 =
  5. 5.78 − 29 =
  6. 6.68 − 29 =
  7. 7.51 − 29 =
  8. 8.90 − 29 =
  9. 9.65 − 9 =
  10. 10.53 + 29 =
  11. 11.866 − 99 =
  12. 12.76 + 29 =
  13. 13.82 − 29 =
  14. 14.50 + 29 =
  15. 15.745 + 99 =
  16. 16.31 + 29 =
  17. 17.16 + 19 =
  18. 18.781 − 99 =
  19. 19.266 − 99 =
  20. 20.76 + 9 =
  21. 21.80 + 19 =
  22. 22.80 − 19 =
  23. 23.56 − 9 =
  24. 24.656 − 99 =
  25. 25.59 − 9 =
  26. 26.31 + 19 =
  27. 27.27 − 19 =
  28. 28.565 − 99 =
  29. 29.59 + 19 =
  30. 30.662 + 99 =
  31. 31.29 − 9 =
  32. 32.49 + 19 =
  33. 33.50 − 29 =
  34. 34.546 + 99 =
  35. 35.21 + 19 =
  36. 36.19 + 29 =
  37. 37.38 + 29 =
  38. 38.676 − 99 =
  39. 39.32 + 19 =
  40. 40.12 + 19 =

Answer key

  1. 12
  2. 711
  3. 41
  4. 424
  5. 49
  6. 39
  7. 22
  8. 61
  9. 56
  10. 82
  11. 767
  12. 105
  13. 53
  14. 79
  15. 844
  16. 60
  17. 35
  18. 682
  19. 167
  20. 85
  21. 99
  22. 61
  23. 47
  24. 557
  25. 50
  26. 50
  27. 8
  28. 466
  29. 78
  30. 761
  31. 20
  32. 68
  33. 21
  34. 645
  35. 40
  36. 48
  37. 67
  38. 577
  39. 51
  40. 31

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