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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 573 · 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. 1.52 − 19 =
  2. 2.49 + 19 =
  3. 3.72 + 29 =
  4. 4.259 − 99 =
  5. 5.62 − 9 =
  6. 6.58 + 9 =
  7. 7.57 + 9 =
  8. 8.41 + 29 =
  9. 9.36 − 29 =
  10. 10.14 + 19 =
  11. 11.652 − 99 =
  12. 12.20 + 29 =
  13. 13.31 − 9 =
  14. 14.39 + 19 =
  15. 15.79 − 9 =
  16. 16.38 − 9 =
  17. 17.34 + 9 =
  18. 18.31 + 9 =
  19. 19.55 + 29 =
  20. 20.83 − 9 =
  21. 21.100 − 29 =
  22. 22.323 + 99 =
  23. 23.462 − 99 =
  24. 24.16 + 29 =
  25. 25.36 + 29 =
  26. 26.52 − 29 =
  27. 27.698 − 99 =
  28. 28.70 + 9 =
  29. 29.80 + 9 =
  30. 30.75 + 19 =
  31. 31.29 − 19 =
  32. 32.452 − 99 =
  33. 33.42 − 9 =
  34. 34.63 − 29 =
  35. 35.107 − 29 =
  36. 36.30 − 9 =
  37. 37.78 − 9 =
  38. 38.573 − 99 =
  39. 39.43 + 19 =
  40. 40.28 + 19 =

Answer key

  1. 33
  2. 68
  3. 101
  4. 160
  5. 53
  6. 67
  7. 66
  8. 70
  9. 7
  10. 33
  11. 553
  12. 49
  13. 22
  14. 58
  15. 70
  16. 29
  17. 43
  18. 40
  19. 84
  20. 74
  21. 71
  22. 422
  23. 363
  24. 45
  25. 65
  26. 23
  27. 599
  28. 79
  29. 89
  30. 94
  31. 10
  32. 353
  33. 33
  34. 34
  35. 78
  36. 21
  37. 69
  38. 474
  39. 62
  40. 47

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