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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 363 · 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. 1.69 + 9 =
  2. 2.51 + 29 =
  3. 3.318 − 99 =
  4. 4.695 + 99 =
  5. 5.342 + 99 =
  6. 6.79 − 29 =
  7. 7.49 − 29 =
  8. 8.403 + 99 =
  9. 9.59 + 9 =
  10. 10.664 + 99 =
  11. 11.31 + 19 =
  12. 12.64 + 9 =
  13. 13.425 + 99 =
  14. 14.87 − 9 =
  15. 15.506 + 99 =
  16. 16.46 + 19 =
  17. 17.40 − 29 =
  18. 18.33 + 29 =
  19. 19.77 − 9 =
  20. 20.44 + 9 =
  21. 21.61 + 19 =
  22. 22.70 + 19 =
  23. 23.14 + 19 =
  24. 24.328 + 99 =
  25. 25.24 + 9 =
  26. 26.85 − 9 =
  27. 27.25 + 9 =
  28. 28.532 − 99 =
  29. 29.41 + 9 =
  30. 30.57 + 29 =
  31. 31.526 − 99 =
  32. 32.817 − 99 =
  33. 33.230 − 99 =
  34. 34.48 − 9 =
  35. 35.40 + 19 =
  36. 36.54 − 19 =
  37. 37.43 + 9 =
  38. 38.170 + 99 =
  39. 39.15 + 29 =
  40. 40.77 + 29 =

Answer key

  1. 78
  2. 80
  3. 219
  4. 794
  5. 441
  6. 50
  7. 20
  8. 502
  9. 68
  10. 763
  11. 50
  12. 73
  13. 524
  14. 78
  15. 605
  16. 65
  17. 11
  18. 62
  19. 68
  20. 53
  21. 80
  22. 89
  23. 33
  24. 427
  25. 33
  26. 76
  27. 34
  28. 433
  29. 50
  30. 86
  31. 427
  32. 718
  33. 131
  34. 39
  35. 59
  36. 35
  37. 52
  38. 269
  39. 44
  40. 106

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