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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 425 · 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. 1.78 − 19 =
  2. 2.52 + 29 =
  3. 3.60 + 19 =
  4. 4.71 + 19 =
  5. 5.60 + 9 =
  6. 6.691 − 99 =
  7. 7.23 − 19 =
  8. 8.62 + 19 =
  9. 9.69 + 29 =
  10. 10.22 + 9 =
  11. 11.63 − 9 =
  12. 12.737 − 99 =
  13. 13.53 − 19 =
  14. 14.56 − 19 =
  15. 15.51 − 19 =
  16. 16.38 + 29 =
  17. 17.51 + 9 =
  18. 18.55 − 19 =
  19. 19.37 − 19 =
  20. 20.17 − 9 =
  21. 21.58 − 29 =
  22. 22.478 − 99 =
  23. 23.651 + 99 =
  24. 24.17 + 9 =
  25. 25.555 + 99 =
  26. 26.24 + 9 =
  27. 27.648 − 99 =
  28. 28.574 − 99 =
  29. 29.39 + 29 =
  30. 30.20 + 9 =
  31. 31.302 + 99 =
  32. 32.59 + 9 =
  33. 33.32 − 19 =
  34. 34.644 + 99 =
  35. 35.373 + 99 =
  36. 36.61 − 29 =
  37. 37.12 + 19 =
  38. 38.40 − 19 =
  39. 39.26 + 9 =
  40. 40.35 − 19 =

Answer key

  1. 59
  2. 81
  3. 79
  4. 90
  5. 69
  6. 592
  7. 4
  8. 81
  9. 98
  10. 31
  11. 54
  12. 638
  13. 34
  14. 37
  15. 32
  16. 67
  17. 60
  18. 36
  19. 18
  20. 8
  21. 29
  22. 379
  23. 750
  24. 26
  25. 654
  26. 33
  27. 549
  28. 475
  29. 68
  30. 29
  31. 401
  32. 68
  33. 13
  34. 743
  35. 472
  36. 32
  37. 31
  38. 21
  39. 35
  40. 16

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