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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 474 · 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. 1.37 + 29 =
  2. 2.29 − 19 =
  3. 3.107 − 29 =
  4. 4.62 + 9 =
  5. 5.47 − 19 =
  6. 6.67 − 9 =
  7. 7.88 − 29 =
  8. 8.75 + 19 =
  9. 9.82 − 19 =
  10. 10.14 + 9 =
  11. 11.17 + 29 =
  12. 12.339 − 99 =
  13. 13.29 + 9 =
  14. 14.520 − 99 =
  15. 15.20 + 19 =
  16. 16.33 + 19 =
  17. 17.15 − 9 =
  18. 18.66 − 29 =
  19. 19.452 + 99 =
  20. 20.48 − 29 =
  21. 21.40 + 9 =
  22. 22.59 − 9 =
  23. 23.75 − 29 =
  24. 24.40 + 29 =
  25. 25.507 − 99 =
  26. 26.26 + 9 =
  27. 27.16 + 9 =
  28. 28.33 − 29 =
  29. 29.24 + 9 =
  30. 30.46 + 19 =
  31. 31.26 + 29 =
  32. 32.76 + 19 =
  33. 33.201 + 99 =
  34. 34.23 − 9 =
  35. 35.13 + 9 =
  36. 36.28 + 9 =
  37. 37.720 + 99 =
  38. 38.30 − 9 =
  39. 39.101 − 29 =
  40. 40.61 + 9 =

Answer key

  1. 66
  2. 10
  3. 78
  4. 71
  5. 28
  6. 58
  7. 59
  8. 94
  9. 63
  10. 23
  11. 46
  12. 240
  13. 38
  14. 421
  15. 39
  16. 52
  17. 6
  18. 37
  19. 551
  20. 19
  21. 49
  22. 50
  23. 46
  24. 69
  25. 408
  26. 35
  27. 25
  28. 4
  29. 33
  30. 65
  31. 55
  32. 95
  33. 300
  34. 14
  35. 22
  36. 37
  37. 819
  38. 21
  39. 72
  40. 70

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