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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 140 · 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. 1.63 − 19 =
  2. 2.47 − 9 =
  3. 3.25 + 19 =
  4. 4.700 + 99 =
  5. 5.32 − 29 =
  6. 6.34 − 19 =
  7. 7.747 + 99 =
  8. 8.37 + 9 =
  9. 9.574 + 99 =
  10. 10.32 − 9 =
  11. 11.36 − 9 =
  12. 12.22 − 19 =
  13. 13.742 + 99 =
  14. 14.346 − 99 =
  15. 15.22 + 9 =
  16. 16.55 + 9 =
  17. 17.189 + 99 =
  18. 18.75 + 19 =
  19. 19.29 + 9 =
  20. 20.80 + 29 =
  21. 21.59 − 9 =
  22. 22.73 − 29 =
  23. 23.88 − 29 =
  24. 24.33 − 19 =
  25. 25.59 + 19 =
  26. 26.62 + 29 =
  27. 27.63 + 9 =
  28. 28.70 − 29 =
  29. 29.78 + 29 =
  30. 30.29 + 29 =
  31. 31.62 + 19 =
  32. 32.87 − 9 =
  33. 33.25 + 29 =
  34. 34.72 − 19 =
  35. 35.33 + 19 =
  36. 36.183 − 99 =
  37. 37.773 + 99 =
  38. 38.561 − 99 =
  39. 39.18 + 9 =
  40. 40.81 − 19 =

Answer key

  1. 44
  2. 38
  3. 44
  4. 799
  5. 3
  6. 15
  7. 846
  8. 46
  9. 673
  10. 23
  11. 27
  12. 3
  13. 841
  14. 247
  15. 31
  16. 64
  17. 288
  18. 94
  19. 38
  20. 109
  21. 50
  22. 44
  23. 59
  24. 14
  25. 78
  26. 91
  27. 72
  28. 41
  29. 107
  30. 58
  31. 81
  32. 78
  33. 54
  34. 53
  35. 52
  36. 84
  37. 872
  38. 462
  39. 27
  40. 62

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