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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 566 · 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. 2.33 + 29 =
  3. 3.48 − 9 =
  4. 4.173 + 99 =
  5. 5.747 + 99 =
  6. 6.104 − 29 =
  7. 7.71 − 29 =
  8. 8.800 − 99 =
  9. 9.26 − 9 =
  10. 10.15 − 9 =
  11. 11.759 − 99 =
  12. 12.65 − 9 =
  13. 13.25 + 19 =
  14. 14.51 + 9 =
  15. 15.499 − 99 =
  16. 16.364 + 99 =
  17. 17.67 + 19 =
  18. 18.36 + 9 =
  19. 19.276 + 99 =
  20. 20.98 − 29 =
  21. 21.14 + 29 =
  22. 22.45 + 29 =
  23. 23.62 + 9 =
  24. 24.27 + 29 =
  25. 25.454 + 99 =
  26. 26.496 − 99 =
  27. 27.44 + 9 =
  28. 28.70 + 19 =
  29. 29.716 − 99 =
  30. 30.56 + 19 =
  31. 31.31 + 19 =
  32. 32.69 − 19 =
  33. 33.75 + 9 =
  34. 34.34 − 9 =
  35. 35.162 − 99 =
  36. 36.147 + 99 =
  37. 37.75 − 9 =
  38. 38.47 − 29 =
  39. 39.94 − 29 =
  40. 40.40 − 9 =

Answer key

  1. 43
  2. 62
  3. 39
  4. 272
  5. 846
  6. 75
  7. 42
  8. 701
  9. 17
  10. 6
  11. 660
  12. 56
  13. 44
  14. 60
  15. 400
  16. 463
  17. 86
  18. 45
  19. 375
  20. 69
  21. 43
  22. 74
  23. 71
  24. 56
  25. 553
  26. 397
  27. 53
  28. 89
  29. 617
  30. 75
  31. 50
  32. 50
  33. 84
  34. 25
  35. 63
  36. 246
  37. 66
  38. 18
  39. 65
  40. 31

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