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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 710 · 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. 1.619 + 99 =
  2. 2.73 + 29 =
  3. 3.50 + 9 =
  4. 4.64 − 19 =
  5. 5.648 − 99 =
  6. 6.80 + 29 =
  7. 7.24 − 19 =
  8. 8.38 + 9 =
  9. 9.556 − 99 =
  10. 10.52 + 29 =
  11. 11.358 − 99 =
  12. 12.624 + 99 =
  13. 13.70 − 9 =
  14. 14.46 + 9 =
  15. 15.80 + 19 =
  16. 16.68 + 19 =
  17. 17.33 + 29 =
  18. 18.32 + 19 =
  19. 19.87 − 9 =
  20. 20.38 − 19 =
  21. 21.900 − 99 =
  22. 22.41 − 29 =
  23. 23.47 + 29 =
  24. 24.37 + 9 =
  25. 25.50 − 29 =
  26. 26.59 − 29 =
  27. 27.108 − 29 =
  28. 28.41 + 19 =
  29. 29.261 − 99 =
  30. 30.66 + 19 =
  31. 31.637 + 99 =
  32. 32.33 + 9 =
  33. 33.247 + 99 =
  34. 34.39 − 19 =
  35. 35.26 + 19 =
  36. 36.661 − 99 =
  37. 37.61 + 19 =
  38. 38.58 − 9 =
  39. 39.15 + 29 =
  40. 40.52 − 29 =

Answer key

  1. 718
  2. 102
  3. 59
  4. 45
  5. 549
  6. 109
  7. 5
  8. 47
  9. 457
  10. 81
  11. 259
  12. 723
  13. 61
  14. 55
  15. 99
  16. 87
  17. 62
  18. 51
  19. 78
  20. 19
  21. 801
  22. 12
  23. 76
  24. 46
  25. 21
  26. 30
  27. 79
  28. 60
  29. 162
  30. 85
  31. 736
  32. 42
  33. 346
  34. 20
  35. 45
  36. 562
  37. 80
  38. 49
  39. 44
  40. 23

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