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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 14 · 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. 1.64 + 9 =
  2. 2.44 − 19 =
  3. 3.49 − 29 =
  4. 4.43 + 19 =
  5. 5.648 − 99 =
  6. 6.58 − 19 =
  7. 7.55 − 9 =
  8. 8.14 + 9 =
  9. 9.66 − 29 =
  10. 10.24 + 19 =
  11. 11.56 + 19 =
  12. 12.61 + 9 =
  13. 13.201 − 99 =
  14. 14.25 + 9 =
  15. 15.61 + 19 =
  16. 16.29 + 19 =
  17. 17.42 + 19 =
  18. 18.28 + 9 =
  19. 19.505 + 99 =
  20. 20.78 + 29 =
  21. 21.56 − 29 =
  22. 22.32 − 19 =
  23. 23.20 − 9 =
  24. 24.37 − 29 =
  25. 25.44 + 9 =
  26. 26.71 − 9 =
  27. 27.565 − 99 =
  28. 28.46 − 19 =
  29. 29.62 + 19 =
  30. 30.18 − 9 =
  31. 31.57 − 19 =
  32. 32.123 + 99 =
  33. 33.652 − 99 =
  34. 34.107 − 29 =
  35. 35.160 + 99 =
  36. 36.349 − 99 =
  37. 37.36 + 9 =
  38. 38.30 − 19 =
  39. 39.20 + 29 =
  40. 40.762 − 99 =

Answer key

  1. 73
  2. 25
  3. 20
  4. 62
  5. 549
  6. 39
  7. 46
  8. 23
  9. 37
  10. 43
  11. 75
  12. 70
  13. 102
  14. 34
  15. 80
  16. 48
  17. 61
  18. 37
  19. 604
  20. 107
  21. 27
  22. 13
  23. 11
  24. 8
  25. 53
  26. 62
  27. 466
  28. 27
  29. 81
  30. 9
  31. 38
  32. 222
  33. 553
  34. 78
  35. 259
  36. 250
  37. 45
  38. 11
  39. 49
  40. 663

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