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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 885 · 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. 1.891 − 99 =
  2. 2.34 − 19 =
  3. 3.43 − 29 =
  4. 4.70 − 19 =
  5. 5.60 + 29 =
  6. 6.41 + 19 =
  7. 7.23 + 29 =
  8. 8.47 + 29 =
  9. 9.71 − 19 =
  10. 10.15 + 29 =
  11. 11.33 + 29 =
  12. 12.23 + 19 =
  13. 13.77 + 19 =
  14. 14.622 − 99 =
  15. 15.14 − 9 =
  16. 16.80 + 9 =
  17. 17.333 − 99 =
  18. 18.200 − 99 =
  19. 19.33 − 29 =
  20. 20.22 + 29 =
  21. 21.27 + 9 =
  22. 22.766 + 99 =
  23. 23.788 + 99 =
  24. 24.12 + 29 =
  25. 25.55 − 9 =
  26. 26.728 − 99 =
  27. 27.17 + 9 =
  28. 28.51 + 29 =
  29. 29.335 + 99 =
  30. 30.63 − 29 =
  31. 31.57 + 19 =
  32. 32.56 + 9 =
  33. 33.40 − 29 =
  34. 34.70 − 9 =
  35. 35.648 + 99 =
  36. 36.572 − 99 =
  37. 37.38 − 19 =
  38. 38.363 + 99 =
  39. 39.60 − 19 =
  40. 40.14 + 9 =

Answer key

  1. 792
  2. 15
  3. 14
  4. 51
  5. 89
  6. 60
  7. 52
  8. 76
  9. 52
  10. 44
  11. 62
  12. 42
  13. 96
  14. 523
  15. 5
  16. 89
  17. 234
  18. 101
  19. 4
  20. 51
  21. 36
  22. 865
  23. 887
  24. 41
  25. 46
  26. 629
  27. 26
  28. 80
  29. 434
  30. 34
  31. 76
  32. 65
  33. 11
  34. 61
  35. 747
  36. 473
  37. 19
  38. 462
  39. 41
  40. 23

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