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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 51 · 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 − 29 =
  2. 2.76 − 19 =
  3. 3.54 + 9 =
  4. 4.33 − 9 =
  5. 5.29 − 19 =
  6. 6.75 + 9 =
  7. 7.660 + 99 =
  8. 8.360 − 99 =
  9. 9.746 − 99 =
  10. 10.644 + 99 =
  11. 11.18 + 9 =
  12. 12.544 − 99 =
  13. 13.368 + 99 =
  14. 14.41 + 29 =
  15. 15.54 + 19 =
  16. 16.41 + 9 =
  17. 17.80 − 9 =
  18. 18.39 + 29 =
  19. 19.625 + 99 =
  20. 20.22 + 29 =
  21. 21.65 + 9 =
  22. 22.28 − 9 =
  23. 23.563 + 99 =
  24. 24.523 + 99 =
  25. 25.45 − 9 =
  26. 26.28 + 29 =
  27. 27.542 − 99 =
  28. 28.12 + 29 =
  29. 29.46 − 9 =
  30. 30.84 − 19 =
  31. 31.39 + 9 =
  32. 32.29 + 9 =
  33. 33.68 + 9 =
  34. 34.45 + 9 =
  35. 35.281 − 99 =
  36. 36.72 + 9 =
  37. 37.366 − 99 =
  38. 38.85 − 19 =
  39. 39.355 − 99 =
  40. 40.25 − 9 =

Answer key

  1. 12
  2. 57
  3. 63
  4. 24
  5. 10
  6. 84
  7. 759
  8. 261
  9. 647
  10. 743
  11. 27
  12. 445
  13. 467
  14. 70
  15. 73
  16. 50
  17. 71
  18. 68
  19. 724
  20. 51
  21. 74
  22. 19
  23. 662
  24. 622
  25. 36
  26. 57
  27. 443
  28. 41
  29. 37
  30. 65
  31. 48
  32. 38
  33. 77
  34. 54
  35. 182
  36. 81
  37. 267
  38. 66
  39. 256
  40. 16

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