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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 441 · 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. 1.60 + 29 =
  2. 2.808 − 99 =
  3. 3.30 + 19 =
  4. 4.35 − 9 =
  5. 5.32 − 19 =
  6. 6.35 + 19 =
  7. 7.37 + 29 =
  8. 8.14 + 9 =
  9. 9.70 − 9 =
  10. 10.78 + 29 =
  11. 11.693 + 99 =
  12. 12.47 + 9 =
  13. 13.632 − 99 =
  14. 14.822 − 99 =
  15. 15.48 − 29 =
  16. 16.51 − 29 =
  17. 17.680 − 99 =
  18. 18.61 − 19 =
  19. 19.192 + 99 =
  20. 20.283 + 99 =
  21. 21.47 + 19 =
  22. 22.36 + 19 =
  23. 23.38 − 19 =
  24. 24.19 + 29 =
  25. 25.57 + 9 =
  26. 26.47 − 19 =
  27. 27.67 − 19 =
  28. 28.28 + 9 =
  29. 29.32 − 9 =
  30. 30.31 − 19 =
  31. 31.61 − 9 =
  32. 32.50 + 9 =
  33. 33.42 − 19 =
  34. 34.30 − 19 =
  35. 35.321 + 99 =
  36. 36.291 − 99 =
  37. 37.51 + 9 =
  38. 38.19 − 9 =
  39. 39.19 + 9 =
  40. 40.69 − 9 =

Answer key

  1. 89
  2. 709
  3. 49
  4. 26
  5. 13
  6. 54
  7. 66
  8. 23
  9. 61
  10. 107
  11. 792
  12. 56
  13. 533
  14. 723
  15. 19
  16. 22
  17. 581
  18. 42
  19. 291
  20. 382
  21. 66
  22. 55
  23. 19
  24. 48
  25. 66
  26. 28
  27. 48
  28. 37
  29. 23
  30. 12
  31. 52
  32. 59
  33. 23
  34. 11
  35. 420
  36. 192
  37. 60
  38. 10
  39. 28
  40. 60

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