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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 289 · 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. 1.52 + 29 =
  2. 2.38 − 29 =
  3. 3.75 + 9 =
  4. 4.23 + 19 =
  5. 5.228 + 99 =
  6. 6.63 − 19 =
  7. 7.51 − 19 =
  8. 8.594 − 99 =
  9. 9.37 + 19 =
  10. 10.34 + 29 =
  11. 11.291 + 99 =
  12. 12.57 − 9 =
  13. 13.367 − 99 =
  14. 14.19 − 9 =
  15. 15.77 + 29 =
  16. 16.23 + 9 =
  17. 17.71 − 19 =
  18. 18.14 + 19 =
  19. 19.66 − 29 =
  20. 20.332 + 99 =
  21. 21.25 − 9 =
  22. 22.633 + 99 =
  23. 23.32 − 9 =
  24. 24.26 − 9 =
  25. 25.78 + 29 =
  26. 26.706 − 99 =
  27. 27.78 + 19 =
  28. 28.833 − 99 =
  29. 29.72 − 9 =
  30. 30.75 − 29 =
  31. 31.62 + 29 =
  32. 32.97 − 29 =
  33. 33.17 − 9 =
  34. 34.65 + 9 =
  35. 35.72 − 29 =
  36. 36.496 − 99 =
  37. 37.13 − 9 =
  38. 38.881 − 99 =
  39. 39.58 + 9 =
  40. 40.26 + 19 =

Answer key

  1. 81
  2. 9
  3. 84
  4. 42
  5. 327
  6. 44
  7. 32
  8. 495
  9. 56
  10. 63
  11. 390
  12. 48
  13. 268
  14. 10
  15. 106
  16. 32
  17. 52
  18. 33
  19. 37
  20. 431
  21. 16
  22. 732
  23. 23
  24. 17
  25. 107
  26. 607
  27. 97
  28. 734
  29. 63
  30. 46
  31. 91
  32. 68
  33. 8
  34. 74
  35. 43
  36. 397
  37. 4
  38. 782
  39. 67
  40. 45

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