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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 559 · 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. 1.78 + 9 =
  2. 2.13 − 9 =
  3. 3.73 − 19 =
  4. 4.70 + 29 =
  5. 5.27 − 9 =
  6. 6.61 + 9 =
  7. 7.58 + 29 =
  8. 8.231 + 99 =
  9. 9.37 − 19 =
  10. 10.28 + 19 =
  11. 11.47 + 9 =
  12. 12.103 − 29 =
  13. 13.41 − 19 =
  14. 14.461 + 99 =
  15. 15.73 + 9 =
  16. 16.161 + 99 =
  17. 17.60 + 29 =
  18. 18.302 + 99 =
  19. 19.67 − 29 =
  20. 20.100 − 29 =
  21. 21.38 + 19 =
  22. 22.68 + 29 =
  23. 23.52 + 29 =
  24. 24.73 + 29 =
  25. 25.37 − 29 =
  26. 26.461 − 99 =
  27. 27.76 − 29 =
  28. 28.32 − 9 =
  29. 29.18 + 19 =
  30. 30.101 − 29 =
  31. 31.268 + 99 =
  32. 32.28 + 29 =
  33. 33.52 + 19 =
  34. 34.277 + 99 =
  35. 35.229 + 99 =
  36. 36.43 − 19 =
  37. 37.49 + 29 =
  38. 38.33 + 29 =
  39. 39.29 + 19 =
  40. 40.22 + 29 =

Answer key

  1. 87
  2. 4
  3. 54
  4. 99
  5. 18
  6. 70
  7. 87
  8. 330
  9. 18
  10. 47
  11. 56
  12. 74
  13. 22
  14. 560
  15. 82
  16. 260
  17. 89
  18. 401
  19. 38
  20. 71
  21. 57
  22. 97
  23. 81
  24. 102
  25. 8
  26. 362
  27. 47
  28. 23
  29. 37
  30. 72
  31. 367
  32. 57
  33. 71
  34. 376
  35. 328
  36. 24
  37. 78
  38. 62
  39. 48
  40. 51

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