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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 867 · 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. 1.20 + 29 =
  2. 2.37 − 19 =
  3. 3.74 − 9 =
  4. 4.23 + 29 =
  5. 5.63 − 29 =
  6. 6.97 − 29 =
  7. 7.21 + 9 =
  8. 8.558 − 99 =
  9. 9.13 + 19 =
  10. 10.242 + 99 =
  11. 11.30 − 19 =
  12. 12.84 − 9 =
  13. 13.213 + 99 =
  14. 14.12 + 19 =
  15. 15.44 − 19 =
  16. 16.33 − 9 =
  17. 17.54 − 9 =
  18. 18.53 − 9 =
  19. 19.34 − 9 =
  20. 20.212 + 99 =
  21. 21.42 + 29 =
  22. 22.32 + 9 =
  23. 23.31 − 9 =
  24. 24.17 + 19 =
  25. 25.27 − 9 =
  26. 26.54 + 19 =
  27. 27.46 + 19 =
  28. 28.38 + 29 =
  29. 29.91 − 19 =
  30. 30.77 + 19 =
  31. 31.376 − 99 =
  32. 32.50 + 9 =
  33. 33.545 + 99 =
  34. 34.44 − 9 =
  35. 35.17 − 9 =
  36. 36.44 + 29 =
  37. 37.325 − 99 =
  38. 38.210 − 99 =
  39. 39.14 + 19 =
  40. 40.86 − 29 =

Answer key

  1. 49
  2. 18
  3. 65
  4. 52
  5. 34
  6. 68
  7. 30
  8. 459
  9. 32
  10. 341
  11. 11
  12. 75
  13. 312
  14. 31
  15. 25
  16. 24
  17. 45
  18. 44
  19. 25
  20. 311
  21. 71
  22. 41
  23. 22
  24. 36
  25. 18
  26. 73
  27. 65
  28. 67
  29. 72
  30. 96
  31. 277
  32. 59
  33. 644
  34. 35
  35. 8
  36. 73
  37. 226
  38. 111
  39. 33
  40. 57

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