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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 959 · 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. 1.31 − 9 =
  2. 2.26 + 9 =
  3. 3.23 − 9 =
  4. 4.86 − 9 =
  5. 5.24 − 9 =
  6. 6.675 − 99 =
  7. 7.63 + 9 =
  8. 8.21 + 29 =
  9. 9.35 − 19 =
  10. 10.560 − 99 =
  11. 11.62 − 19 =
  12. 12.20 − 9 =
  13. 13.444 + 99 =
  14. 14.56 + 29 =
  15. 15.28 − 9 =
  16. 16.50 − 29 =
  17. 17.40 + 9 =
  18. 18.58 − 9 =
  19. 19.118 + 99 =
  20. 20.19 + 9 =
  21. 21.78 − 19 =
  22. 22.18 − 9 =
  23. 23.500 + 99 =
  24. 24.12 + 29 =
  25. 25.14 − 9 =
  26. 26.542 + 99 =
  27. 27.65 − 19 =
  28. 28.61 + 19 =
  29. 29.54 + 29 =
  30. 30.72 + 9 =
  31. 31.86 − 29 =
  32. 32.55 + 29 =
  33. 33.18 + 19 =
  34. 34.76 − 9 =
  35. 35.52 + 9 =
  36. 36.802 − 99 =
  37. 37.22 + 19 =
  38. 38.12 + 9 =
  39. 39.97 − 29 =
  40. 40.21 + 9 =

Answer key

  1. 22
  2. 35
  3. 14
  4. 77
  5. 15
  6. 576
  7. 72
  8. 50
  9. 16
  10. 461
  11. 43
  12. 11
  13. 543
  14. 85
  15. 19
  16. 21
  17. 49
  18. 49
  19. 217
  20. 28
  21. 59
  22. 9
  23. 599
  24. 41
  25. 5
  26. 641
  27. 46
  28. 80
  29. 83
  30. 81
  31. 57
  32. 84
  33. 37
  34. 67
  35. 61
  36. 703
  37. 41
  38. 21
  39. 68
  40. 30

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