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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 454 · 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. 1.32 − 19 =
  2. 2.47 + 9 =
  3. 3.55 − 19 =
  4. 4.77 + 29 =
  5. 5.770 − 99 =
  6. 6.74 − 19 =
  7. 7.56 + 29 =
  8. 8.96 − 19 =
  9. 9.46 + 9 =
  10. 10.41 + 19 =
  11. 11.48 + 29 =
  12. 12.38 + 19 =
  13. 13.387 + 99 =
  14. 14.748 + 99 =
  15. 15.18 + 19 =
  16. 16.57 + 9 =
  17. 17.102 − 29 =
  18. 18.78 − 9 =
  19. 19.36 + 19 =
  20. 20.25 + 29 =
  21. 21.31 + 9 =
  22. 22.750 − 99 =
  23. 23.65 − 19 =
  24. 24.24 + 9 =
  25. 25.69 + 29 =
  26. 26.34 + 19 =
  27. 27.14 + 29 =
  28. 28.25 − 9 =
  29. 29.28 − 19 =
  30. 30.76 − 29 =
  31. 31.39 + 9 =
  32. 32.41 + 29 =
  33. 33.68 − 19 =
  34. 34.13 − 9 =
  35. 35.672 + 99 =
  36. 36.30 + 19 =
  37. 37.67 + 9 =
  38. 38.48 − 29 =
  39. 39.37 − 9 =
  40. 40.19 + 9 =

Answer key

  1. 13
  2. 56
  3. 36
  4. 106
  5. 671
  6. 55
  7. 85
  8. 77
  9. 55
  10. 60
  11. 77
  12. 57
  13. 486
  14. 847
  15. 37
  16. 66
  17. 73
  18. 69
  19. 55
  20. 54
  21. 40
  22. 651
  23. 46
  24. 33
  25. 98
  26. 53
  27. 43
  28. 16
  29. 9
  30. 47
  31. 48
  32. 70
  33. 49
  34. 4
  35. 771
  36. 49
  37. 76
  38. 19
  39. 28
  40. 28

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