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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 368 · 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. 2.46 + 29 =
  3. 3.79 − 9 =
  4. 4.80 + 19 =
  5. 5.189 + 99 =
  6. 6.18 − 9 =
  7. 7.26 + 29 =
  8. 8.45 − 29 =
  9. 9.482 − 99 =
  10. 10.664 − 99 =
  11. 11.96 − 29 =
  12. 12.73 + 9 =
  13. 13.174 − 99 =
  14. 14.46 − 19 =
  15. 15.28 + 9 =
  16. 16.27 + 9 =
  17. 17.64 − 9 =
  18. 18.56 + 9 =
  19. 19.41 − 29 =
  20. 20.86 − 19 =
  21. 21.92 − 19 =
  22. 22.657 − 99 =
  23. 23.36 − 29 =
  24. 24.331 − 99 =
  25. 25.76 − 19 =
  26. 26.58 + 19 =
  27. 27.446 + 99 =
  28. 28.514 + 99 =
  29. 29.20 + 9 =
  30. 30.36 − 19 =
  31. 31.62 + 9 =
  32. 32.49 + 29 =
  33. 33.671 + 99 =
  34. 34.247 − 99 =
  35. 35.423 − 99 =
  36. 36.581 − 99 =
  37. 37.80 + 29 =
  38. 38.37 − 29 =
  39. 39.33 + 19 =
  40. 40.240 + 99 =

Answer key

  1. 59
  2. 75
  3. 70
  4. 99
  5. 288
  6. 9
  7. 55
  8. 16
  9. 383
  10. 565
  11. 67
  12. 82
  13. 75
  14. 27
  15. 37
  16. 36
  17. 55
  18. 65
  19. 12
  20. 67
  21. 73
  22. 558
  23. 7
  24. 232
  25. 57
  26. 77
  27. 545
  28. 613
  29. 29
  30. 17
  31. 71
  32. 78
  33. 770
  34. 148
  35. 324
  36. 482
  37. 109
  38. 8
  39. 52
  40. 339

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