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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 915 · 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. 1.29 + 29 =
  2. 2.229 + 99 =
  3. 3.184 − 99 =
  4. 4.94 − 19 =
  5. 5.47 + 29 =
  6. 6.36 + 19 =
  7. 7.30 + 19 =
  8. 8.76 + 29 =
  9. 9.57 + 9 =
  10. 10.12 + 29 =
  11. 11.47 − 9 =
  12. 12.44 + 19 =
  13. 13.82 − 19 =
  14. 14.32 − 19 =
  15. 15.80 + 19 =
  16. 16.65 + 29 =
  17. 17.40 − 19 =
  18. 18.67 + 29 =
  19. 19.64 + 29 =
  20. 20.658 + 99 =
  21. 21.31 + 29 =
  22. 22.51 + 9 =
  23. 23.898 − 99 =
  24. 24.59 − 19 =
  25. 25.65 + 9 =
  26. 26.280 + 99 =
  27. 27.821 − 99 =
  28. 28.603 + 99 =
  29. 29.42 − 29 =
  30. 30.19 + 29 =
  31. 31.532 − 99 =
  32. 32.84 − 29 =
  33. 33.59 − 29 =
  34. 34.31 + 19 =
  35. 35.32 − 29 =
  36. 36.27 − 9 =
  37. 37.66 + 9 =
  38. 38.72 + 29 =
  39. 39.363 − 99 =
  40. 40.249 + 99 =

Answer key

  1. 58
  2. 328
  3. 85
  4. 75
  5. 76
  6. 55
  7. 49
  8. 105
  9. 66
  10. 41
  11. 38
  12. 63
  13. 63
  14. 13
  15. 99
  16. 94
  17. 21
  18. 96
  19. 93
  20. 757
  21. 60
  22. 60
  23. 799
  24. 40
  25. 74
  26. 379
  27. 722
  28. 702
  29. 13
  30. 48
  31. 433
  32. 55
  33. 30
  34. 50
  35. 3
  36. 18
  37. 75
  38. 101
  39. 264
  40. 348

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