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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 423 · 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. 1.39 + 19 =
  2. 2.29 + 19 =
  3. 3.43 + 9 =
  4. 4.51 + 9 =
  5. 5.70 − 19 =
  6. 6.720 + 99 =
  7. 7.466 + 99 =
  8. 8.57 + 9 =
  9. 9.18 − 9 =
  10. 10.72 + 9 =
  11. 11.240 − 99 =
  12. 12.36 − 9 =
  13. 13.82 − 9 =
  14. 14.56 − 19 =
  15. 15.107 − 29 =
  16. 16.13 + 19 =
  17. 17.75 + 9 =
  18. 18.58 + 9 =
  19. 19.13 + 29 =
  20. 20.79 + 19 =
  21. 21.723 − 99 =
  22. 22.50 + 9 =
  23. 23.76 + 9 =
  24. 24.21 + 29 =
  25. 25.813 − 99 =
  26. 26.62 + 9 =
  27. 27.31 + 29 =
  28. 28.576 + 99 =
  29. 29.85 − 19 =
  30. 30.68 + 19 =
  31. 31.80 − 9 =
  32. 32.36 + 19 =
  33. 33.32 + 29 =
  34. 34.14 − 9 =
  35. 35.36 + 9 =
  36. 36.792 − 99 =
  37. 37.76 − 9 =
  38. 38.34 + 19 =
  39. 39.435 − 99 =
  40. 40.67 − 29 =

Answer key

  1. 58
  2. 48
  3. 52
  4. 60
  5. 51
  6. 819
  7. 565
  8. 66
  9. 9
  10. 81
  11. 141
  12. 27
  13. 73
  14. 37
  15. 78
  16. 32
  17. 84
  18. 67
  19. 42
  20. 98
  21. 624
  22. 59
  23. 85
  24. 50
  25. 714
  26. 71
  27. 60
  28. 675
  29. 66
  30. 87
  31. 71
  32. 55
  33. 61
  34. 5
  35. 45
  36. 693
  37. 67
  38. 53
  39. 336
  40. 38

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