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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 184 · 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. 1.57 + 9 =
  2. 2.662 + 99 =
  3. 3.88 − 29 =
  4. 4.497 − 99 =
  5. 5.46 + 9 =
  6. 6.67 − 9 =
  7. 7.99 − 29 =
  8. 8.74 − 9 =
  9. 9.142 + 99 =
  10. 10.21 + 9 =
  11. 11.105 + 99 =
  12. 12.16 + 29 =
  13. 13.242 + 99 =
  14. 14.78 − 19 =
  15. 15.378 + 99 =
  16. 16.87 − 9 =
  17. 17.67 − 19 =
  18. 18.37 − 9 =
  19. 19.59 − 29 =
  20. 20.26 + 9 =
  21. 21.63 + 9 =
  22. 22.78 − 9 =
  23. 23.41 − 9 =
  24. 24.717 + 99 =
  25. 25.45 + 9 =
  26. 26.688 + 99 =
  27. 27.778 + 99 =
  28. 28.26 − 19 =
  29. 29.18 + 9 =
  30. 30.24 + 9 =
  31. 31.60 − 9 =
  32. 32.512 − 99 =
  33. 33.28 + 19 =
  34. 34.63 + 29 =
  35. 35.389 − 99 =
  36. 36.52 + 19 =
  37. 37.57 − 9 =
  38. 38.33 + 29 =
  39. 39.815 − 99 =
  40. 40.17 − 9 =

Answer key

  1. 66
  2. 761
  3. 59
  4. 398
  5. 55
  6. 58
  7. 70
  8. 65
  9. 241
  10. 30
  11. 204
  12. 45
  13. 341
  14. 59
  15. 477
  16. 78
  17. 48
  18. 28
  19. 30
  20. 35
  21. 72
  22. 69
  23. 32
  24. 816
  25. 54
  26. 787
  27. 877
  28. 7
  29. 27
  30. 33
  31. 51
  32. 413
  33. 47
  34. 92
  35. 290
  36. 71
  37. 48
  38. 62
  39. 716
  40. 8

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