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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 742 · 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. 1.24 − 19 =
  2. 2.25 + 9 =
  3. 3.70 − 29 =
  4. 4.40 + 19 =
  5. 5.27 + 19 =
  6. 6.22 + 9 =
  7. 7.28 − 19 =
  8. 8.45 − 9 =
  9. 9.76 − 19 =
  10. 10.457 − 99 =
  11. 11.93 − 19 =
  12. 12.34 − 29 =
  13. 13.22 − 19 =
  14. 14.59 − 9 =
  15. 15.43 − 29 =
  16. 16.705 − 99 =
  17. 17.51 + 9 =
  18. 18.29 + 19 =
  19. 19.52 + 9 =
  20. 20.559 − 99 =
  21. 21.24 + 29 =
  22. 22.64 + 9 =
  23. 23.49 + 19 =
  24. 24.46 + 29 =
  25. 25.372 + 99 =
  26. 26.54 − 29 =
  27. 27.407 + 99 =
  28. 28.48 + 29 =
  29. 29.68 − 19 =
  30. 30.46 − 9 =
  31. 31.67 − 19 =
  32. 32.79 + 29 =
  33. 33.72 − 29 =
  34. 34.91 − 19 =
  35. 35.42 + 9 =
  36. 36.30 + 29 =
  37. 37.84 − 19 =
  38. 38.61 + 9 =
  39. 39.48 + 9 =
  40. 40.246 − 99 =

Answer key

  1. 5
  2. 34
  3. 41
  4. 59
  5. 46
  6. 31
  7. 9
  8. 36
  9. 57
  10. 358
  11. 74
  12. 5
  13. 3
  14. 50
  15. 14
  16. 606
  17. 60
  18. 48
  19. 61
  20. 460
  21. 53
  22. 73
  23. 68
  24. 75
  25. 471
  26. 25
  27. 506
  28. 77
  29. 49
  30. 37
  31. 48
  32. 108
  33. 43
  34. 72
  35. 51
  36. 59
  37. 65
  38. 70
  39. 57
  40. 147

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