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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 540 · 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. 1.698 − 99 =
  2. 2.34 + 9 =
  3. 3.29 + 19 =
  4. 4.73 − 29 =
  5. 5.21 + 9 =
  6. 6.151 − 99 =
  7. 7.26 − 9 =
  8. 8.70 + 9 =
  9. 9.73 + 9 =
  10. 10.60 − 9 =
  11. 11.414 − 99 =
  12. 12.51 + 29 =
  13. 13.73 + 19 =
  14. 14.522 + 99 =
  15. 15.71 + 19 =
  16. 16.14 + 19 =
  17. 17.40 − 29 =
  18. 18.48 + 19 =
  19. 19.93 − 29 =
  20. 20.38 + 29 =
  21. 21.187 + 99 =
  22. 22.38 − 9 =
  23. 23.86 − 9 =
  24. 24.45 − 19 =
  25. 25.693 − 99 =
  26. 26.35 + 29 =
  27. 27.242 + 99 =
  28. 28.56 − 19 =
  29. 29.64 − 9 =
  30. 30.46 − 9 =
  31. 31.65 + 9 =
  32. 32.422 + 99 =
  33. 33.543 − 99 =
  34. 34.19 + 9 =
  35. 35.24 − 9 =
  36. 36.63 + 29 =
  37. 37.47 − 29 =
  38. 38.80 − 29 =
  39. 39.27 + 19 =
  40. 40.56 + 19 =

Answer key

  1. 599
  2. 43
  3. 48
  4. 44
  5. 30
  6. 52
  7. 17
  8. 79
  9. 82
  10. 51
  11. 315
  12. 80
  13. 92
  14. 621
  15. 90
  16. 33
  17. 11
  18. 67
  19. 64
  20. 67
  21. 286
  22. 29
  23. 77
  24. 26
  25. 594
  26. 64
  27. 341
  28. 37
  29. 55
  30. 37
  31. 74
  32. 521
  33. 444
  34. 28
  35. 15
  36. 92
  37. 18
  38. 51
  39. 46
  40. 75

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