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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 82 · 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. 1.695 + 99 =
  2. 2.52 + 9 =
  3. 3.13 − 9 =
  4. 4.896 − 99 =
  5. 5.60 + 9 =
  6. 6.71 + 29 =
  7. 7.77 − 29 =
  8. 8.21 + 9 =
  9. 9.52 − 19 =
  10. 10.35 + 19 =
  11. 11.27 + 29 =
  12. 12.51 + 9 =
  13. 13.428 + 99 =
  14. 14.33 + 29 =
  15. 15.34 − 9 =
  16. 16.61 − 9 =
  17. 17.47 + 19 =
  18. 18.249 − 99 =
  19. 19.239 − 99 =
  20. 20.27 − 9 =
  21. 21.20 + 9 =
  22. 22.36 + 9 =
  23. 23.43 − 29 =
  24. 24.788 − 99 =
  25. 25.69 − 29 =
  26. 26.35 − 9 =
  27. 27.92 − 29 =
  28. 28.54 − 19 =
  29. 29.26 + 9 =
  30. 30.40 − 19 =
  31. 31.70 + 9 =
  32. 32.55 + 9 =
  33. 33.14 + 29 =
  34. 34.686 − 99 =
  35. 35.60 + 29 =
  36. 36.75 − 19 =
  37. 37.284 − 99 =
  38. 38.27 + 19 =
  39. 39.62 + 19 =
  40. 40.72 + 19 =

Answer key

  1. 794
  2. 61
  3. 4
  4. 797
  5. 69
  6. 100
  7. 48
  8. 30
  9. 33
  10. 54
  11. 56
  12. 60
  13. 527
  14. 62
  15. 25
  16. 52
  17. 66
  18. 150
  19. 140
  20. 18
  21. 29
  22. 45
  23. 14
  24. 689
  25. 40
  26. 26
  27. 63
  28. 35
  29. 35
  30. 21
  31. 79
  32. 64
  33. 43
  34. 587
  35. 89
  36. 56
  37. 185
  38. 46
  39. 81
  40. 91

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