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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 635 · 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. 1.54 + 9 =
  2. 2.772 − 99 =
  3. 3.63 − 9 =
  4. 4.39 − 19 =
  5. 5.286 + 99 =
  6. 6.303 − 99 =
  7. 7.42 − 19 =
  8. 8.55 − 9 =
  9. 9.64 − 19 =
  10. 10.18 + 19 =
  11. 11.72 − 9 =
  12. 12.14 + 29 =
  13. 13.38 + 19 =
  14. 14.52 + 19 =
  15. 15.87 − 9 =
  16. 16.24 + 9 =
  17. 17.315 − 99 =
  18. 18.60 − 29 =
  19. 19.74 + 19 =
  20. 20.70 + 29 =
  21. 21.251 − 99 =
  22. 22.704 − 99 =
  23. 23.22 + 29 =
  24. 24.55 + 29 =
  25. 25.68 + 9 =
  26. 26.429 + 99 =
  27. 27.41 + 19 =
  28. 28.43 + 9 =
  29. 29.101 − 29 =
  30. 30.14 + 9 =
  31. 31.23 + 9 =
  32. 32.277 − 99 =
  33. 33.38 − 19 =
  34. 34.12 − 9 =
  35. 35.709 + 99 =
  36. 36.53 − 9 =
  37. 37.103 − 29 =
  38. 38.277 + 99 =
  39. 39.24 + 19 =
  40. 40.54 + 19 =

Answer key

  1. 63
  2. 673
  3. 54
  4. 20
  5. 385
  6. 204
  7. 23
  8. 46
  9. 45
  10. 37
  11. 63
  12. 43
  13. 57
  14. 71
  15. 78
  16. 33
  17. 216
  18. 31
  19. 93
  20. 99
  21. 152
  22. 605
  23. 51
  24. 84
  25. 77
  26. 528
  27. 60
  28. 52
  29. 72
  30. 23
  31. 32
  32. 178
  33. 19
  34. 3
  35. 808
  36. 44
  37. 74
  38. 376
  39. 43
  40. 73

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