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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 298 · 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. 1.22 + 19 =
  2. 2.23 − 9 =
  3. 3.69 + 29 =
  4. 4.15 + 19 =
  5. 5.224 + 99 =
  6. 6.49 + 19 =
  7. 7.154 + 99 =
  8. 8.73 − 19 =
  9. 9.678 − 99 =
  10. 10.16 − 9 =
  11. 11.62 + 9 =
  12. 12.31 + 29 =
  13. 13.184 + 99 =
  14. 14.499 + 99 =
  15. 15.175 + 99 =
  16. 16.94 − 19 =
  17. 17.27 + 9 =
  18. 18.59 + 9 =
  19. 19.85 − 19 =
  20. 20.28 + 19 =
  21. 21.14 − 9 =
  22. 22.63 − 9 =
  23. 23.74 + 9 =
  24. 24.64 + 9 =
  25. 25.37 + 9 =
  26. 26.12 + 29 =
  27. 27.47 + 19 =
  28. 28.54 + 29 =
  29. 29.39 + 29 =
  30. 30.117 + 99 =
  31. 31.734 − 99 =
  32. 32.23 + 29 =
  33. 33.32 − 29 =
  34. 34.29 + 19 =
  35. 35.60 − 19 =
  36. 36.95 − 19 =
  37. 37.803 − 99 =
  38. 38.20 + 19 =
  39. 39.32 − 9 =
  40. 40.16 + 9 =

Answer key

  1. 41
  2. 14
  3. 98
  4. 34
  5. 323
  6. 68
  7. 253
  8. 54
  9. 579
  10. 7
  11. 71
  12. 60
  13. 283
  14. 598
  15. 274
  16. 75
  17. 36
  18. 68
  19. 66
  20. 47
  21. 5
  22. 54
  23. 83
  24. 73
  25. 46
  26. 41
  27. 66
  28. 83
  29. 68
  30. 216
  31. 635
  32. 52
  33. 3
  34. 48
  35. 41
  36. 76
  37. 704
  38. 39
  39. 23
  40. 25

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