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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 926 · 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. 1.27 + 29 =
  2. 2.451 + 99 =
  3. 3.427 + 99 =
  4. 4.280 + 99 =
  5. 5.42 + 9 =
  6. 6.62 + 29 =
  7. 7.84 − 9 =
  8. 8.77 − 19 =
  9. 9.105 + 99 =
  10. 10.49 − 29 =
  11. 11.58 − 19 =
  12. 12.23 − 19 =
  13. 13.17 + 9 =
  14. 14.20 − 9 =
  15. 15.368 + 99 =
  16. 16.586 + 99 =
  17. 17.591 − 99 =
  18. 18.56 − 19 =
  19. 19.28 − 9 =
  20. 20.76 + 9 =
  21. 21.17 + 29 =
  22. 22.797 − 99 =
  23. 23.12 + 29 =
  24. 24.80 + 19 =
  25. 25.259 − 99 =
  26. 26.693 + 99 =
  27. 27.106 − 29 =
  28. 28.739 − 99 =
  29. 29.179 − 99 =
  30. 30.18 + 19 =
  31. 31.87 − 9 =
  32. 32.51 + 29 =
  33. 33.47 + 9 =
  34. 34.68 − 9 =
  35. 35.192 − 99 =
  36. 36.35 + 29 =
  37. 37.54 + 9 =
  38. 38.580 − 99 =
  39. 39.46 − 29 =
  40. 40.30 − 9 =

Answer key

  1. 56
  2. 550
  3. 526
  4. 379
  5. 51
  6. 91
  7. 75
  8. 58
  9. 204
  10. 20
  11. 39
  12. 4
  13. 26
  14. 11
  15. 467
  16. 685
  17. 492
  18. 37
  19. 19
  20. 85
  21. 46
  22. 698
  23. 41
  24. 99
  25. 160
  26. 792
  27. 77
  28. 640
  29. 80
  30. 37
  31. 78
  32. 80
  33. 56
  34. 59
  35. 93
  36. 64
  37. 63
  38. 481
  39. 17
  40. 21

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