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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 377 · 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. 1.61 + 9 =
  2. 2.32 + 19 =
  3. 3.480 + 99 =
  4. 4.297 + 99 =
  5. 5.238 − 99 =
  6. 6.41 − 19 =
  7. 7.497 − 99 =
  8. 8.24 + 29 =
  9. 9.40 + 19 =
  10. 10.39 + 29 =
  11. 11.120 + 99 =
  12. 12.52 + 19 =
  13. 13.23 − 9 =
  14. 14.62 + 19 =
  15. 15.22 + 9 =
  16. 16.773 + 99 =
  17. 17.285 − 99 =
  18. 18.17 − 9 =
  19. 19.90 − 19 =
  20. 20.80 + 29 =
  21. 21.32 + 9 =
  22. 22.30 − 19 =
  23. 23.647 + 99 =
  24. 24.59 − 29 =
  25. 25.35 − 9 =
  26. 26.16 + 29 =
  27. 27.784 − 99 =
  28. 28.26 − 19 =
  29. 29.50 + 19 =
  30. 30.27 − 9 =
  31. 31.417 − 99 =
  32. 32.79 + 9 =
  33. 33.63 + 29 =
  34. 34.848 − 99 =
  35. 35.749 − 99 =
  36. 36.258 + 99 =
  37. 37.384 + 99 =
  38. 38.635 + 99 =
  39. 39.55 + 29 =
  40. 40.37 + 9 =

Answer key

  1. 70
  2. 51
  3. 579
  4. 396
  5. 139
  6. 22
  7. 398
  8. 53
  9. 59
  10. 68
  11. 219
  12. 71
  13. 14
  14. 81
  15. 31
  16. 872
  17. 186
  18. 8
  19. 71
  20. 109
  21. 41
  22. 11
  23. 746
  24. 30
  25. 26
  26. 45
  27. 685
  28. 7
  29. 69
  30. 18
  31. 318
  32. 88
  33. 92
  34. 749
  35. 650
  36. 357
  37. 483
  38. 734
  39. 84
  40. 46

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