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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 818 · 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. 1.56 − 19 =
  2. 2.12 + 9 =
  3. 3.19 + 19 =
  4. 4.72 − 29 =
  5. 5.67 − 9 =
  6. 6.534 + 99 =
  7. 7.76 + 19 =
  8. 8.71 + 19 =
  9. 9.17 − 9 =
  10. 10.37 + 29 =
  11. 11.27 − 19 =
  12. 12.26 + 9 =
  13. 13.61 + 29 =
  14. 14.532 + 99 =
  15. 15.99 − 29 =
  16. 16.39 + 19 =
  17. 17.77 − 19 =
  18. 18.231 − 99 =
  19. 19.12 + 29 =
  20. 20.71 + 9 =
  21. 21.45 + 29 =
  22. 22.604 − 99 =
  23. 23.13 − 9 =
  24. 24.208 − 99 =
  25. 25.855 − 99 =
  26. 26.62 + 29 =
  27. 27.41 − 9 =
  28. 28.53 − 29 =
  29. 29.450 − 99 =
  30. 30.48 − 19 =
  31. 31.28 − 9 =
  32. 32.26 + 29 =
  33. 33.74 + 19 =
  34. 34.54 − 9 =
  35. 35.109 − 29 =
  36. 36.82 − 9 =
  37. 37.51 + 29 =
  38. 38.25 − 9 =
  39. 39.21 + 9 =
  40. 40.31 + 9 =

Answer key

  1. 37
  2. 21
  3. 38
  4. 43
  5. 58
  6. 633
  7. 95
  8. 90
  9. 8
  10. 66
  11. 8
  12. 35
  13. 90
  14. 631
  15. 70
  16. 58
  17. 58
  18. 132
  19. 41
  20. 80
  21. 74
  22. 505
  23. 4
  24. 109
  25. 756
  26. 91
  27. 32
  28. 24
  29. 351
  30. 29
  31. 19
  32. 55
  33. 93
  34. 45
  35. 80
  36. 73
  37. 80
  38. 16
  39. 30
  40. 40

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