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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 670 · 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. 1.42 + 9 =
  2. 2.645 + 99 =
  3. 3.64 + 29 =
  4. 4.80 + 9 =
  5. 5.19 + 19 =
  6. 6.38 + 19 =
  7. 7.31 + 19 =
  8. 8.47 + 9 =
  9. 9.394 − 99 =
  10. 10.13 + 19 =
  11. 11.62 + 9 =
  12. 12.58 − 19 =
  13. 13.493 + 99 =
  14. 14.384 + 99 =
  15. 15.30 − 9 =
  16. 16.509 + 99 =
  17. 17.30 + 9 =
  18. 18.283 + 99 =
  19. 19.43 + 19 =
  20. 20.89 − 29 =
  21. 21.68 − 29 =
  22. 22.58 + 29 =
  23. 23.57 − 19 =
  24. 24.27 + 9 =
  25. 25.56 − 29 =
  26. 26.28 + 29 =
  27. 27.102 − 29 =
  28. 28.53 + 19 =
  29. 29.490 + 99 =
  30. 30.440 − 99 =
  31. 31.88 − 19 =
  32. 32.44 + 9 =
  33. 33.36 + 9 =
  34. 34.65 − 9 =
  35. 35.53 + 9 =
  36. 36.14 − 9 =
  37. 37.106 − 29 =
  38. 38.75 − 9 =
  39. 39.57 + 9 =
  40. 40.20 + 19 =

Answer key

  1. 51
  2. 744
  3. 93
  4. 89
  5. 38
  6. 57
  7. 50
  8. 56
  9. 295
  10. 32
  11. 71
  12. 39
  13. 592
  14. 483
  15. 21
  16. 608
  17. 39
  18. 382
  19. 62
  20. 60
  21. 39
  22. 87
  23. 38
  24. 36
  25. 27
  26. 57
  27. 73
  28. 72
  29. 589
  30. 341
  31. 69
  32. 53
  33. 45
  34. 56
  35. 62
  36. 5
  37. 77
  38. 66
  39. 66
  40. 39

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