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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 570 · 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. 1.210 + 99 =
  2. 2.20 + 19 =
  3. 3.22 + 19 =
  4. 4.26 + 9 =
  5. 5.24 + 19 =
  6. 6.17 + 9 =
  7. 7.34 + 29 =
  8. 8.66 + 9 =
  9. 9.89 − 29 =
  10. 10.79 + 9 =
  11. 11.56 − 19 =
  12. 12.23 + 9 =
  13. 13.83 − 29 =
  14. 14.42 + 9 =
  15. 15.705 + 99 =
  16. 16.605 + 99 =
  17. 17.70 + 9 =
  18. 18.15 + 9 =
  19. 19.105 + 99 =
  20. 20.663 + 99 =
  21. 21.18 + 29 =
  22. 22.439 + 99 =
  23. 23.51 − 9 =
  24. 24.80 + 19 =
  25. 25.231 + 99 =
  26. 26.53 + 19 =
  27. 27.32 + 9 =
  28. 28.467 − 99 =
  29. 29.324 + 99 =
  30. 30.82 − 9 =
  31. 31.80 + 9 =
  32. 32.19 − 9 =
  33. 33.62 + 19 =
  34. 34.78 − 19 =
  35. 35.96 − 19 =
  36. 36.32 − 19 =
  37. 37.65 + 19 =
  38. 38.19 + 19 =
  39. 39.154 − 99 =
  40. 40.96 − 29 =

Answer key

  1. 309
  2. 39
  3. 41
  4. 35
  5. 43
  6. 26
  7. 63
  8. 75
  9. 60
  10. 88
  11. 37
  12. 32
  13. 54
  14. 51
  15. 804
  16. 704
  17. 79
  18. 24
  19. 204
  20. 762
  21. 47
  22. 538
  23. 42
  24. 99
  25. 330
  26. 72
  27. 41
  28. 368
  29. 423
  30. 73
  31. 89
  32. 10
  33. 81
  34. 59
  35. 77
  36. 13
  37. 84
  38. 38
  39. 55
  40. 67

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