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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 962 · 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. 1.52 + 9 =
  2. 2.71 + 29 =
  3. 3.293 − 99 =
  4. 4.63 + 29 =
  5. 5.34 − 9 =
  6. 6.96 − 19 =
  7. 7.738 − 99 =
  8. 8.45 + 19 =
  9. 9.436 − 99 =
  10. 10.14 + 19 =
  11. 11.852 − 99 =
  12. 12.32 − 9 =
  13. 13.67 + 9 =
  14. 14.20 + 9 =
  15. 15.63 − 29 =
  16. 16.78 + 9 =
  17. 17.662 − 99 =
  18. 18.225 + 99 =
  19. 19.51 − 19 =
  20. 20.515 + 99 =
  21. 21.371 − 99 =
  22. 22.58 + 19 =
  23. 23.19 + 29 =
  24. 24.60 + 9 =
  25. 25.33 + 9 =
  26. 26.15 + 29 =
  27. 27.755 − 99 =
  28. 28.109 − 29 =
  29. 29.740 + 99 =
  30. 30.15 + 19 =
  31. 31.30 + 9 =
  32. 32.64 − 29 =
  33. 33.138 + 99 =
  34. 34.84 − 29 =
  35. 35.104 − 29 =
  36. 36.470 − 99 =
  37. 37.38 − 29 =
  38. 38.32 + 9 =
  39. 39.31 + 9 =
  40. 40.583 + 99 =

Answer key

  1. 61
  2. 100
  3. 194
  4. 92
  5. 25
  6. 77
  7. 639
  8. 64
  9. 337
  10. 33
  11. 753
  12. 23
  13. 76
  14. 29
  15. 34
  16. 87
  17. 563
  18. 324
  19. 32
  20. 614
  21. 272
  22. 77
  23. 48
  24. 69
  25. 42
  26. 44
  27. 656
  28. 80
  29. 839
  30. 34
  31. 39
  32. 35
  33. 237
  34. 55
  35. 75
  36. 371
  37. 9
  38. 41
  39. 40
  40. 682

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