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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 369 · 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. 1.63 − 19 =
  2. 2.18 + 19 =
  3. 3.53 − 29 =
  4. 4.32 − 19 =
  5. 5.19 − 9 =
  6. 6.232 − 99 =
  7. 7.51 − 29 =
  8. 8.705 + 99 =
  9. 9.72 − 29 =
  10. 10.85 − 29 =
  11. 11.16 − 9 =
  12. 12.33 − 9 =
  13. 13.12 + 9 =
  14. 14.68 + 9 =
  15. 15.27 + 9 =
  16. 16.328 − 99 =
  17. 17.56 + 19 =
  18. 18.74 + 9 =
  19. 19.69 − 9 =
  20. 20.104 − 29 =
  21. 21.35 + 29 =
  22. 22.573 − 99 =
  23. 23.369 + 99 =
  24. 24.704 − 99 =
  25. 25.66 + 9 =
  26. 26.30 + 9 =
  27. 27.27 − 19 =
  28. 28.59 − 19 =
  29. 29.89 − 9 =
  30. 30.79 − 19 =
  31. 31.62 + 19 =
  32. 32.381 + 99 =
  33. 33.209 − 99 =
  34. 34.29 + 29 =
  35. 35.43 + 9 =
  36. 36.54 + 29 =
  37. 37.75 − 19 =
  38. 38.41 − 29 =
  39. 39.71 + 29 =
  40. 40.67 − 9 =

Answer key

  1. 44
  2. 37
  3. 24
  4. 13
  5. 10
  6. 133
  7. 22
  8. 804
  9. 43
  10. 56
  11. 7
  12. 24
  13. 21
  14. 77
  15. 36
  16. 229
  17. 75
  18. 83
  19. 60
  20. 75
  21. 64
  22. 474
  23. 468
  24. 605
  25. 75
  26. 39
  27. 8
  28. 40
  29. 80
  30. 60
  31. 81
  32. 480
  33. 110
  34. 58
  35. 52
  36. 83
  37. 56
  38. 12
  39. 100
  40. 58

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