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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 408 · 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. 1.72 + 9 =
  2. 2.777 − 99 =
  3. 3.28 − 9 =
  4. 4.72 + 29 =
  5. 5.12 + 9 =
  6. 6.38 − 29 =
  7. 7.529 + 99 =
  8. 8.27 + 19 =
  9. 9.59 + 9 =
  10. 10.47 + 19 =
  11. 11.93 − 29 =
  12. 12.79 + 29 =
  13. 13.48 + 29 =
  14. 14.643 − 99 =
  15. 15.51 + 29 =
  16. 16.712 − 99 =
  17. 17.94 − 29 =
  18. 18.55 + 19 =
  19. 19.27 − 9 =
  20. 20.31 + 29 =
  21. 21.15 + 19 =
  22. 22.606 + 99 =
  23. 23.34 − 29 =
  24. 24.98 − 29 =
  25. 25.693 + 99 =
  26. 26.42 + 19 =
  27. 27.82 − 19 =
  28. 28.96 − 29 =
  29. 29.58 + 19 =
  30. 30.54 + 9 =
  31. 31.44 − 19 =
  32. 32.30 + 29 =
  33. 33.178 + 99 =
  34. 34.71 + 19 =
  35. 35.80 + 9 =
  36. 36.71 − 19 =
  37. 37.302 − 99 =
  38. 38.23 + 19 =
  39. 39.45 − 29 =
  40. 40.109 − 29 =

Answer key

  1. 81
  2. 678
  3. 19
  4. 101
  5. 21
  6. 9
  7. 628
  8. 46
  9. 68
  10. 66
  11. 64
  12. 108
  13. 77
  14. 544
  15. 80
  16. 613
  17. 65
  18. 74
  19. 18
  20. 60
  21. 34
  22. 705
  23. 5
  24. 69
  25. 792
  26. 61
  27. 63
  28. 67
  29. 77
  30. 63
  31. 25
  32. 59
  33. 277
  34. 90
  35. 89
  36. 52
  37. 203
  38. 42
  39. 16
  40. 80

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