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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 503 · 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. 1.42 − 19 =
  2. 2.48 + 9 =
  3. 3.94 − 19 =
  4. 4.73 − 9 =
  5. 5.48 − 29 =
  6. 6.48 − 19 =
  7. 7.24 + 29 =
  8. 8.64 − 9 =
  9. 9.354 − 99 =
  10. 10.29 − 9 =
  11. 11.20 − 9 =
  12. 12.67 − 29 =
  13. 13.32 − 19 =
  14. 14.74 + 29 =
  15. 15.66 − 19 =
  16. 16.32 − 9 =
  17. 17.40 − 19 =
  18. 18.661 − 99 =
  19. 19.457 + 99 =
  20. 20.251 − 99 =
  21. 21.19 + 9 =
  22. 22.78 + 29 =
  23. 23.41 + 9 =
  24. 24.238 + 99 =
  25. 25.35 + 9 =
  26. 26.24 + 19 =
  27. 27.517 − 99 =
  28. 28.39 − 19 =
  29. 29.23 + 19 =
  30. 30.98 − 29 =
  31. 31.68 + 29 =
  32. 32.768 + 99 =
  33. 33.14 − 9 =
  34. 34.48 − 9 =
  35. 35.85 − 9 =
  36. 36.41 + 29 =
  37. 37.86 − 19 =
  38. 38.58 + 9 =
  39. 39.672 − 99 =
  40. 40.826 − 99 =

Answer key

  1. 23
  2. 57
  3. 75
  4. 64
  5. 19
  6. 29
  7. 53
  8. 55
  9. 255
  10. 20
  11. 11
  12. 38
  13. 13
  14. 103
  15. 47
  16. 23
  17. 21
  18. 562
  19. 556
  20. 152
  21. 28
  22. 107
  23. 50
  24. 337
  25. 44
  26. 43
  27. 418
  28. 20
  29. 42
  30. 69
  31. 97
  32. 867
  33. 5
  34. 39
  35. 76
  36. 70
  37. 67
  38. 67
  39. 573
  40. 727

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