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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 716 · 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. 1.47 + 9 =
  2. 2.12 + 19 =
  3. 3.246 + 99 =
  4. 4.64 + 19 =
  5. 5.67 − 29 =
  6. 6.20 + 9 =
  7. 7.73 − 29 =
  8. 8.33 + 9 =
  9. 9.27 − 9 =
  10. 10.419 − 99 =
  11. 11.735 − 99 =
  12. 12.420 + 99 =
  13. 13.97 − 19 =
  14. 14.68 + 19 =
  15. 15.46 − 9 =
  16. 16.68 − 29 =
  17. 17.23 − 19 =
  18. 18.28 + 19 =
  19. 19.37 − 19 =
  20. 20.85 − 29 =
  21. 21.55 + 9 =
  22. 22.66 − 9 =
  23. 23.106 − 29 =
  24. 24.186 + 99 =
  25. 25.17 + 19 =
  26. 26.43 + 29 =
  27. 27.36 − 19 =
  28. 28.55 + 19 =
  29. 29.344 + 99 =
  30. 30.31 + 9 =
  31. 31.38 − 9 =
  32. 32.59 + 29 =
  33. 33.56 − 19 =
  34. 34.42 − 29 =
  35. 35.263 + 99 =
  36. 36.676 − 99 =
  37. 37.38 + 9 =
  38. 38.515 + 99 =
  39. 39.549 − 99 =
  40. 40.42 − 9 =

Answer key

  1. 56
  2. 31
  3. 345
  4. 83
  5. 38
  6. 29
  7. 44
  8. 42
  9. 18
  10. 320
  11. 636
  12. 519
  13. 78
  14. 87
  15. 37
  16. 39
  17. 4
  18. 47
  19. 18
  20. 56
  21. 64
  22. 57
  23. 77
  24. 285
  25. 36
  26. 72
  27. 17
  28. 74
  29. 443
  30. 40
  31. 29
  32. 88
  33. 37
  34. 13
  35. 362
  36. 577
  37. 47
  38. 614
  39. 450
  40. 33

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