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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 590 · 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. 1.109 − 29 =
  2. 2.47 − 29 =
  3. 3.742 + 99 =
  4. 4.68 + 29 =
  5. 5.61 − 19 =
  6. 6.60 − 9 =
  7. 7.20 + 9 =
  8. 8.36 + 9 =
  9. 9.51 + 9 =
  10. 10.50 − 29 =
  11. 11.15 + 19 =
  12. 12.314 − 99 =
  13. 13.19 − 9 =
  14. 14.78 − 9 =
  15. 15.59 + 29 =
  16. 16.90 − 29 =
  17. 17.21 + 29 =
  18. 18.42 − 29 =
  19. 19.600 + 99 =
  20. 20.503 + 99 =
  21. 21.579 + 99 =
  22. 22.86 − 29 =
  23. 23.47 − 19 =
  24. 24.408 + 99 =
  25. 25.781 + 99 =
  26. 26.72 + 19 =
  27. 27.14 − 9 =
  28. 28.52 + 9 =
  29. 29.59 − 29 =
  30. 30.26 − 9 =
  31. 31.13 + 19 =
  32. 32.28 + 19 =
  33. 33.658 + 99 =
  34. 34.37 + 9 =
  35. 35.30 − 19 =
  36. 36.53 − 29 =
  37. 37.59 + 19 =
  38. 38.530 + 99 =
  39. 39.18 − 9 =
  40. 40.22 + 9 =

Answer key

  1. 80
  2. 18
  3. 841
  4. 97
  5. 42
  6. 51
  7. 29
  8. 45
  9. 60
  10. 21
  11. 34
  12. 215
  13. 10
  14. 69
  15. 88
  16. 61
  17. 50
  18. 13
  19. 699
  20. 602
  21. 678
  22. 57
  23. 28
  24. 507
  25. 880
  26. 91
  27. 5
  28. 61
  29. 30
  30. 17
  31. 32
  32. 47
  33. 757
  34. 46
  35. 11
  36. 24
  37. 78
  38. 629
  39. 9
  40. 31

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