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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 254 · 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. 1.41 + 19 =
  2. 2.48 − 9 =
  3. 3.91 − 19 =
  4. 4.54 − 9 =
  5. 5.41 + 9 =
  6. 6.65 − 29 =
  7. 7.752 − 99 =
  8. 8.14 + 9 =
  9. 9.161 + 99 =
  10. 10.71 − 29 =
  11. 11.64 − 9 =
  12. 12.540 − 99 =
  13. 13.812 − 99 =
  14. 14.67 + 19 =
  15. 15.248 − 99 =
  16. 16.42 − 9 =
  17. 17.31 + 9 =
  18. 18.38 − 9 =
  19. 19.70 − 9 =
  20. 20.204 + 99 =
  21. 21.71 − 19 =
  22. 22.20 + 9 =
  23. 23.43 + 9 =
  24. 24.48 + 9 =
  25. 25.651 − 99 =
  26. 26.35 − 9 =
  27. 27.700 + 99 =
  28. 28.76 + 19 =
  29. 29.40 + 9 =
  30. 30.83 − 19 =
  31. 31.230 + 99 =
  32. 32.57 + 29 =
  33. 33.334 + 99 =
  34. 34.40 − 19 =
  35. 35.609 + 99 =
  36. 36.44 − 19 =
  37. 37.168 + 99 =
  38. 38.29 + 9 =
  39. 39.68 − 19 =
  40. 40.75 + 19 =

Answer key

  1. 60
  2. 39
  3. 72
  4. 45
  5. 50
  6. 36
  7. 653
  8. 23
  9. 260
  10. 42
  11. 55
  12. 441
  13. 713
  14. 86
  15. 149
  16. 33
  17. 40
  18. 29
  19. 61
  20. 303
  21. 52
  22. 29
  23. 52
  24. 57
  25. 552
  26. 26
  27. 799
  28. 95
  29. 49
  30. 64
  31. 329
  32. 86
  33. 433
  34. 21
  35. 708
  36. 25
  37. 267
  38. 38
  39. 49
  40. 94

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