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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 426 · 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. 1.19 + 29 =
  2. 2.37 + 9 =
  3. 3.47 + 19 =
  4. 4.23 − 9 =
  5. 5.24 + 9 =
  6. 6.65 + 9 =
  7. 7.106 − 29 =
  8. 8.30 + 29 =
  9. 9.33 − 9 =
  10. 10.61 − 29 =
  11. 11.52 + 9 =
  12. 12.61 + 9 =
  13. 13.429 + 99 =
  14. 14.76 + 19 =
  15. 15.60 + 19 =
  16. 16.39 + 19 =
  17. 17.522 − 99 =
  18. 18.32 + 9 =
  19. 19.21 − 9 =
  20. 20.55 + 19 =
  21. 21.49 + 29 =
  22. 22.43 − 29 =
  23. 23.514 + 99 =
  24. 24.779 − 99 =
  25. 25.22 + 9 =
  26. 26.71 + 9 =
  27. 27.13 − 9 =
  28. 28.29 + 9 =
  29. 29.430 − 99 =
  30. 30.63 + 9 =
  31. 31.54 + 19 =
  32. 32.73 − 19 =
  33. 33.67 − 9 =
  34. 34.60 − 9 =
  35. 35.64 + 19 =
  36. 36.293 − 99 =
  37. 37.293 + 99 =
  38. 38.660 + 99 =
  39. 39.303 + 99 =
  40. 40.30 + 19 =

Answer key

  1. 48
  2. 46
  3. 66
  4. 14
  5. 33
  6. 74
  7. 77
  8. 59
  9. 24
  10. 32
  11. 61
  12. 70
  13. 528
  14. 95
  15. 79
  16. 58
  17. 423
  18. 41
  19. 12
  20. 74
  21. 78
  22. 14
  23. 613
  24. 680
  25. 31
  26. 80
  27. 4
  28. 38
  29. 331
  30. 72
  31. 73
  32. 54
  33. 58
  34. 51
  35. 83
  36. 194
  37. 392
  38. 759
  39. 402
  40. 49

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