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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 964 · 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. 1.778 + 99 =
  2. 2.71 − 9 =
  3. 3.672 − 99 =
  4. 4.44 − 29 =
  5. 5.70 + 29 =
  6. 6.576 + 99 =
  7. 7.653 + 99 =
  8. 8.23 + 19 =
  9. 9.38 − 29 =
  10. 10.37 − 9 =
  11. 11.35 − 9 =
  12. 12.39 + 19 =
  13. 13.72 − 29 =
  14. 14.75 − 29 =
  15. 15.562 + 99 =
  16. 16.22 + 19 =
  17. 17.24 + 19 =
  18. 18.51 + 19 =
  19. 19.37 − 19 =
  20. 20.572 − 99 =
  21. 21.60 − 9 =
  22. 22.63 − 19 =
  23. 23.45 + 9 =
  24. 24.253 + 99 =
  25. 25.74 − 29 =
  26. 26.32 − 19 =
  27. 27.175 − 99 =
  28. 28.491 + 99 =
  29. 29.248 + 99 =
  30. 30.436 − 99 =
  31. 31.62 − 19 =
  32. 32.53 − 29 =
  33. 33.52 + 19 =
  34. 34.29 + 29 =
  35. 35.28 + 9 =
  36. 36.46 − 19 =
  37. 37.86 − 9 =
  38. 38.20 + 19 =
  39. 39.55 + 19 =
  40. 40.65 + 19 =

Answer key

  1. 877
  2. 62
  3. 573
  4. 15
  5. 99
  6. 675
  7. 752
  8. 42
  9. 9
  10. 28
  11. 26
  12. 58
  13. 43
  14. 46
  15. 661
  16. 41
  17. 43
  18. 70
  19. 18
  20. 473
  21. 51
  22. 44
  23. 54
  24. 352
  25. 45
  26. 13
  27. 76
  28. 590
  29. 347
  30. 337
  31. 43
  32. 24
  33. 71
  34. 58
  35. 37
  36. 27
  37. 77
  38. 39
  39. 74
  40. 84

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