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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 85 · 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. 1.15 + 9 =
  2. 2.54 + 29 =
  3. 3.628 + 99 =
  4. 4.65 − 19 =
  5. 5.30 + 29 =
  6. 6.19 − 9 =
  7. 7.43 − 19 =
  8. 8.51 + 9 =
  9. 9.416 − 99 =
  10. 10.15 + 29 =
  11. 11.65 + 29 =
  12. 12.17 − 9 =
  13. 13.61 − 29 =
  14. 14.497 − 99 =
  15. 15.52 + 9 =
  16. 16.12 + 9 =
  17. 17.74 + 9 =
  18. 18.573 + 99 =
  19. 19.79 + 9 =
  20. 20.46 − 9 =
  21. 21.45 + 9 =
  22. 22.60 + 9 =
  23. 23.22 + 19 =
  24. 24.201 + 99 =
  25. 25.18 + 9 =
  26. 26.95 − 19 =
  27. 27.62 − 9 =
  28. 28.20 − 9 =
  29. 29.318 − 99 =
  30. 30.37 − 29 =
  31. 31.73 + 9 =
  32. 32.36 + 29 =
  33. 33.684 − 99 =
  34. 34.77 + 9 =
  35. 35.43 − 29 =
  36. 36.60 − 9 =
  37. 37.658 − 99 =
  38. 38.55 + 9 =
  39. 39.226 + 99 =
  40. 40.35 − 29 =

Answer key

  1. 24
  2. 83
  3. 727
  4. 46
  5. 59
  6. 10
  7. 24
  8. 60
  9. 317
  10. 44
  11. 94
  12. 8
  13. 32
  14. 398
  15. 61
  16. 21
  17. 83
  18. 672
  19. 88
  20. 37
  21. 54
  22. 69
  23. 41
  24. 300
  25. 27
  26. 76
  27. 53
  28. 11
  29. 219
  30. 8
  31. 82
  32. 65
  33. 585
  34. 86
  35. 14
  36. 51
  37. 559
  38. 64
  39. 325
  40. 6

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