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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 271 · 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. 1.595 + 99 =
  2. 2.37 − 9 =
  3. 3.594 + 99 =
  4. 4.63 + 9 =
  5. 5.60 + 19 =
  6. 6.473 − 99 =
  7. 7.28 + 9 =
  8. 8.41 − 19 =
  9. 9.20 + 29 =
  10. 10.26 + 19 =
  11. 11.53 + 29 =
  12. 12.81 − 29 =
  13. 13.46 + 19 =
  14. 14.76 + 9 =
  15. 15.103 − 29 =
  16. 16.399 − 99 =
  17. 17.78 − 19 =
  18. 18.700 + 99 =
  19. 19.36 + 19 =
  20. 20.695 − 99 =
  21. 21.70 + 9 =
  22. 22.71 + 9 =
  23. 23.287 + 99 =
  24. 24.82 − 29 =
  25. 25.898 − 99 =
  26. 26.54 − 19 =
  27. 27.29 − 9 =
  28. 28.34 + 19 =
  29. 29.39 + 9 =
  30. 30.66 − 9 =
  31. 31.27 + 29 =
  32. 32.58 − 19 =
  33. 33.51 + 19 =
  34. 34.375 + 99 =
  35. 35.51 − 29 =
  36. 36.675 − 99 =
  37. 37.852 − 99 =
  38. 38.59 + 9 =
  39. 39.62 − 9 =
  40. 40.12 + 29 =

Answer key

  1. 694
  2. 28
  3. 693
  4. 72
  5. 79
  6. 374
  7. 37
  8. 22
  9. 49
  10. 45
  11. 82
  12. 52
  13. 65
  14. 85
  15. 74
  16. 300
  17. 59
  18. 799
  19. 55
  20. 596
  21. 79
  22. 80
  23. 386
  24. 53
  25. 799
  26. 35
  27. 20
  28. 53
  29. 48
  30. 57
  31. 56
  32. 39
  33. 70
  34. 474
  35. 22
  36. 576
  37. 753
  38. 68
  39. 53
  40. 41

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