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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 618 · 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. 1.376 − 99 =
  2. 2.48 − 9 =
  3. 3.521 − 99 =
  4. 4.598 − 99 =
  5. 5.177 − 99 =
  6. 6.36 − 19 =
  7. 7.84 − 29 =
  8. 8.64 + 19 =
  9. 9.307 + 99 =
  10. 10.96 − 29 =
  11. 11.63 − 19 =
  12. 12.248 − 99 =
  13. 13.33 − 9 =
  14. 14.737 − 99 =
  15. 15.35 + 29 =
  16. 16.518 − 99 =
  17. 17.18 − 9 =
  18. 18.35 − 9 =
  19. 19.448 − 99 =
  20. 20.53 − 19 =
  21. 21.679 + 99 =
  22. 22.54 + 9 =
  23. 23.615 − 99 =
  24. 24.85 − 9 =
  25. 25.51 − 19 =
  26. 26.55 + 29 =
  27. 27.650 + 99 =
  28. 28.59 − 9 =
  29. 29.34 − 19 =
  30. 30.61 − 9 =
  31. 31.64 − 19 =
  32. 32.79 − 29 =
  33. 33.28 + 29 =
  34. 34.28 + 9 =
  35. 35.75 + 19 =
  36. 36.69 − 19 =
  37. 37.33 + 9 =
  38. 38.40 + 19 =
  39. 39.42 − 29 =
  40. 40.48 + 29 =

Answer key

  1. 277
  2. 39
  3. 422
  4. 499
  5. 78
  6. 17
  7. 55
  8. 83
  9. 406
  10. 67
  11. 44
  12. 149
  13. 24
  14. 638
  15. 64
  16. 419
  17. 9
  18. 26
  19. 349
  20. 34
  21. 778
  22. 63
  23. 516
  24. 76
  25. 32
  26. 84
  27. 749
  28. 50
  29. 15
  30. 52
  31. 45
  32. 50
  33. 57
  34. 37
  35. 94
  36. 50
  37. 42
  38. 59
  39. 13
  40. 77

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