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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 836 · 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. 1.75 + 9 =
  2. 2.280 + 99 =
  3. 3.81 − 29 =
  4. 4.107 + 99 =
  5. 5.55 − 9 =
  6. 6.78 + 29 =
  7. 7.33 + 9 =
  8. 8.72 − 19 =
  9. 9.82 − 19 =
  10. 10.103 − 29 =
  11. 11.22 − 9 =
  12. 12.57 − 29 =
  13. 13.69 − 19 =
  14. 14.49 + 19 =
  15. 15.37 − 19 =
  16. 16.107 − 29 =
  17. 17.16 + 9 =
  18. 18.818 − 99 =
  19. 19.71 + 19 =
  20. 20.46 − 29 =
  21. 21.526 + 99 =
  22. 22.695 + 99 =
  23. 23.26 + 9 =
  24. 24.63 − 19 =
  25. 25.25 − 19 =
  26. 26.96 − 19 =
  27. 27.29 − 9 =
  28. 28.841 − 99 =
  29. 29.99 − 19 =
  30. 30.25 + 9 =
  31. 31.759 + 99 =
  32. 32.92 − 19 =
  33. 33.18 − 9 =
  34. 34.82 − 9 =
  35. 35.737 − 99 =
  36. 36.80 − 19 =
  37. 37.68 + 29 =
  38. 38.32 − 29 =
  39. 39.86 − 29 =
  40. 40.17 + 19 =

Answer key

  1. 84
  2. 379
  3. 52
  4. 206
  5. 46
  6. 107
  7. 42
  8. 53
  9. 63
  10. 74
  11. 13
  12. 28
  13. 50
  14. 68
  15. 18
  16. 78
  17. 25
  18. 719
  19. 90
  20. 17
  21. 625
  22. 794
  23. 35
  24. 44
  25. 6
  26. 77
  27. 20
  28. 742
  29. 80
  30. 34
  31. 858
  32. 73
  33. 9
  34. 73
  35. 638
  36. 61
  37. 97
  38. 3
  39. 57
  40. 36

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