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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 409 · 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. 1.74 − 9 =
  2. 2.95 − 19 =
  3. 3.22 + 19 =
  4. 4.92 − 19 =
  5. 5.47 + 29 =
  6. 6.72 − 19 =
  7. 7.66 − 9 =
  8. 8.35 − 29 =
  9. 9.29 + 19 =
  10. 10.522 − 99 =
  11. 11.62 + 19 =
  12. 12.38 + 19 =
  13. 13.47 − 29 =
  14. 14.22 + 29 =
  15. 15.60 − 19 =
  16. 16.54 + 9 =
  17. 17.32 − 29 =
  18. 18.34 − 19 =
  19. 19.22 − 9 =
  20. 20.64 + 9 =
  21. 21.34 − 29 =
  22. 22.23 − 19 =
  23. 23.46 + 9 =
  24. 24.24 + 9 =
  25. 25.56 + 19 =
  26. 26.14 + 29 =
  27. 27.77 + 19 =
  28. 28.38 − 9 =
  29. 29.77 + 9 =
  30. 30.774 − 99 =
  31. 31.64 − 9 =
  32. 32.76 + 29 =
  33. 33.80 − 29 =
  34. 34.61 − 29 =
  35. 35.33 − 9 =
  36. 36.27 + 19 =
  37. 37.20 + 19 =
  38. 38.26 − 19 =
  39. 39.48 − 19 =
  40. 40.98 − 19 =

Answer key

  1. 65
  2. 76
  3. 41
  4. 73
  5. 76
  6. 53
  7. 57
  8. 6
  9. 48
  10. 423
  11. 81
  12. 57
  13. 18
  14. 51
  15. 41
  16. 63
  17. 3
  18. 15
  19. 13
  20. 73
  21. 5
  22. 4
  23. 55
  24. 33
  25. 75
  26. 43
  27. 96
  28. 29
  29. 86
  30. 675
  31. 55
  32. 105
  33. 51
  34. 32
  35. 24
  36. 46
  37. 39
  38. 7
  39. 29
  40. 79

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