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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 752 · 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. 1.79 − 19 =
  2. 2.36 + 9 =
  3. 3.91 − 29 =
  4. 4.78 + 19 =
  5. 5.632 − 99 =
  6. 6.62 − 19 =
  7. 7.708 + 99 =
  8. 8.33 + 29 =
  9. 9.50 + 19 =
  10. 10.33 + 9 =
  11. 11.77 + 9 =
  12. 12.45 − 19 =
  13. 13.15 + 29 =
  14. 14.46 − 19 =
  15. 15.476 − 99 =
  16. 16.35 − 29 =
  17. 17.27 + 29 =
  18. 18.31 − 19 =
  19. 19.91 − 19 =
  20. 20.80 + 19 =
  21. 21.20 − 9 =
  22. 22.97 − 19 =
  23. 23.27 − 19 =
  24. 24.34 − 29 =
  25. 25.52 + 9 =
  26. 26.352 + 99 =
  27. 27.145 + 99 =
  28. 28.94 − 29 =
  29. 29.230 − 99 =
  30. 30.756 + 99 =
  31. 31.46 + 19 =
  32. 32.53 + 19 =
  33. 33.706 + 99 =
  34. 34.26 + 9 =
  35. 35.46 − 29 =
  36. 36.48 + 9 =
  37. 37.32 + 19 =
  38. 38.71 − 19 =
  39. 39.71 + 19 =
  40. 40.43 − 19 =

Answer key

  1. 60
  2. 45
  3. 62
  4. 97
  5. 533
  6. 43
  7. 807
  8. 62
  9. 69
  10. 42
  11. 86
  12. 26
  13. 44
  14. 27
  15. 377
  16. 6
  17. 56
  18. 12
  19. 72
  20. 99
  21. 11
  22. 78
  23. 8
  24. 5
  25. 61
  26. 451
  27. 244
  28. 65
  29. 131
  30. 855
  31. 65
  32. 72
  33. 805
  34. 35
  35. 17
  36. 57
  37. 51
  38. 52
  39. 90
  40. 24

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