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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 737 · 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. 1.98 − 19 =
  2. 2.54 − 9 =
  3. 3.36 − 29 =
  4. 4.55 + 29 =
  5. 5.34 + 9 =
  6. 6.51 − 9 =
  7. 7.75 + 29 =
  8. 8.23 + 29 =
  9. 9.80 + 19 =
  10. 10.236 + 99 =
  11. 11.447 − 99 =
  12. 12.17 + 29 =
  13. 13.132 + 99 =
  14. 14.60 − 9 =
  15. 15.63 + 9 =
  16. 16.98 − 29 =
  17. 17.664 + 99 =
  18. 18.34 + 29 =
  19. 19.96 − 29 =
  20. 20.16 + 9 =
  21. 21.62 − 9 =
  22. 22.59 − 9 =
  23. 23.41 + 29 =
  24. 24.12 + 19 =
  25. 25.502 + 99 =
  26. 26.52 − 9 =
  27. 27.212 + 99 =
  28. 28.20 − 9 =
  29. 29.216 + 99 =
  30. 30.15 − 9 =
  31. 31.64 − 29 =
  32. 32.31 + 29 =
  33. 33.48 + 29 =
  34. 34.196 − 99 =
  35. 35.68 − 29 =
  36. 36.73 + 19 =
  37. 37.739 + 99 =
  38. 38.50 + 29 =
  39. 39.476 + 99 =
  40. 40.95 − 29 =

Answer key

  1. 79
  2. 45
  3. 7
  4. 84
  5. 43
  6. 42
  7. 104
  8. 52
  9. 99
  10. 335
  11. 348
  12. 46
  13. 231
  14. 51
  15. 72
  16. 69
  17. 763
  18. 63
  19. 67
  20. 25
  21. 53
  22. 50
  23. 70
  24. 31
  25. 601
  26. 43
  27. 311
  28. 11
  29. 315
  30. 6
  31. 35
  32. 60
  33. 77
  34. 97
  35. 39
  36. 92
  37. 838
  38. 79
  39. 575
  40. 66

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