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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 84 · 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. 1.16 + 29 =
  2. 2.219 + 99 =
  3. 3.89 − 29 =
  4. 4.29 + 29 =
  5. 5.101 − 29 =
  6. 6.78 + 9 =
  7. 7.24 + 9 =
  8. 8.93 − 29 =
  9. 9.190 − 99 =
  10. 10.589 + 99 =
  11. 11.616 + 99 =
  12. 12.42 + 19 =
  13. 13.38 − 19 =
  14. 14.32 − 29 =
  15. 15.12 − 9 =
  16. 16.34 + 29 =
  17. 17.25 + 9 =
  18. 18.698 + 99 =
  19. 19.29 − 19 =
  20. 20.15 + 9 =
  21. 21.32 + 9 =
  22. 22.36 + 29 =
  23. 23.65 − 29 =
  24. 24.58 + 29 =
  25. 25.53 + 29 =
  26. 26.41 − 19 =
  27. 27.237 − 99 =
  28. 28.25 − 9 =
  29. 29.41 + 19 =
  30. 30.26 − 9 =
  31. 31.74 + 19 =
  32. 32.359 + 99 =
  33. 33.40 − 29 =
  34. 34.19 + 19 =
  35. 35.65 + 29 =
  36. 36.21 + 9 =
  37. 37.67 − 19 =
  38. 38.37 − 9 =
  39. 39.77 + 9 =
  40. 40.265 + 99 =

Answer key

  1. 45
  2. 318
  3. 60
  4. 58
  5. 72
  6. 87
  7. 33
  8. 64
  9. 91
  10. 688
  11. 715
  12. 61
  13. 19
  14. 3
  15. 3
  16. 63
  17. 34
  18. 797
  19. 10
  20. 24
  21. 41
  22. 65
  23. 36
  24. 87
  25. 82
  26. 22
  27. 138
  28. 16
  29. 60
  30. 17
  31. 93
  32. 458
  33. 11
  34. 38
  35. 94
  36. 30
  37. 48
  38. 28
  39. 86
  40. 364

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