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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 250 · 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. 1.41 − 19 =
  2. 2.43 + 9 =
  3. 3.150 − 99 =
  4. 4.63 + 19 =
  5. 5.58 + 29 =
  6. 6.255 + 99 =
  7. 7.52 − 9 =
  8. 8.23 + 19 =
  9. 9.95 − 29 =
  10. 10.42 + 29 =
  11. 11.243 + 99 =
  12. 12.44 + 9 =
  13. 13.42 + 9 =
  14. 14.20 + 19 =
  15. 15.76 − 29 =
  16. 16.77 + 29 =
  17. 17.15 + 29 =
  18. 18.73 + 9 =
  19. 19.55 + 19 =
  20. 20.873 − 99 =
  21. 21.60 − 29 =
  22. 22.13 + 9 =
  23. 23.199 + 99 =
  24. 24.17 + 29 =
  25. 25.462 + 99 =
  26. 26.32 + 9 =
  27. 27.797 + 99 =
  28. 28.671 − 99 =
  29. 29.822 − 99 =
  30. 30.508 + 99 =
  31. 31.21 − 9 =
  32. 32.21 + 9 =
  33. 33.54 − 9 =
  34. 34.93 − 29 =
  35. 35.31 + 19 =
  36. 36.63 − 19 =
  37. 37.74 − 9 =
  38. 38.868 − 99 =
  39. 39.160 − 99 =
  40. 40.548 + 99 =

Answer key

  1. 22
  2. 52
  3. 51
  4. 82
  5. 87
  6. 354
  7. 43
  8. 42
  9. 66
  10. 71
  11. 342
  12. 53
  13. 51
  14. 39
  15. 47
  16. 106
  17. 44
  18. 82
  19. 74
  20. 774
  21. 31
  22. 22
  23. 298
  24. 46
  25. 561
  26. 41
  27. 896
  28. 572
  29. 723
  30. 607
  31. 12
  32. 30
  33. 45
  34. 64
  35. 50
  36. 44
  37. 65
  38. 769
  39. 61
  40. 647

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