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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 612 · 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. 1.23 + 9 =
  2. 2.175 + 99 =
  3. 3.251 − 99 =
  4. 4.64 − 9 =
  5. 5.643 + 99 =
  6. 6.79 + 29 =
  7. 7.13 + 19 =
  8. 8.486 + 99 =
  9. 9.42 + 19 =
  10. 10.290 − 99 =
  11. 11.64 + 19 =
  12. 12.559 + 99 =
  13. 13.36 + 29 =
  14. 14.60 − 9 =
  15. 15.600 + 99 =
  16. 16.40 + 9 =
  17. 17.748 + 99 =
  18. 18.30 − 9 =
  19. 19.44 + 29 =
  20. 20.19 + 19 =
  21. 21.85 − 9 =
  22. 22.207 + 99 =
  23. 23.31 + 19 =
  24. 24.17 + 29 =
  25. 25.59 − 19 =
  26. 26.41 − 19 =
  27. 27.47 − 9 =
  28. 28.645 − 99 =
  29. 29.80 + 29 =
  30. 30.60 + 19 =
  31. 31.792 − 99 =
  32. 32.75 − 19 =
  33. 33.80 + 9 =
  34. 34.374 + 99 =
  35. 35.87 − 9 =
  36. 36.68 + 9 =
  37. 37.20 − 9 =
  38. 38.20 + 19 =
  39. 39.45 + 19 =
  40. 40.684 + 99 =

Answer key

  1. 32
  2. 274
  3. 152
  4. 55
  5. 742
  6. 108
  7. 32
  8. 585
  9. 61
  10. 191
  11. 83
  12. 658
  13. 65
  14. 51
  15. 699
  16. 49
  17. 847
  18. 21
  19. 73
  20. 38
  21. 76
  22. 306
  23. 50
  24. 46
  25. 40
  26. 22
  27. 38
  28. 546
  29. 109
  30. 79
  31. 693
  32. 56
  33. 89
  34. 473
  35. 78
  36. 77
  37. 11
  38. 39
  39. 64
  40. 783

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