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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 461 · 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. 1.20 + 29 =
  2. 2.49 + 29 =
  3. 3.55 + 9 =
  4. 4.45 + 9 =
  5. 5.79 + 19 =
  6. 6.24 − 19 =
  7. 7.29 + 9 =
  8. 8.31 + 9 =
  9. 9.34 + 9 =
  10. 10.416 + 99 =
  11. 11.90 − 19 =
  12. 12.63 − 9 =
  13. 13.75 + 19 =
  14. 14.97 − 29 =
  15. 15.530 − 99 =
  16. 16.40 − 29 =
  17. 17.83 − 29 =
  18. 18.67 + 19 =
  19. 19.43 + 29 =
  20. 20.33 − 29 =
  21. 21.776 + 99 =
  22. 22.68 + 19 =
  23. 23.22 + 29 =
  24. 24.74 + 29 =
  25. 25.49 − 29 =
  26. 26.19 + 9 =
  27. 27.786 + 99 =
  28. 28.78 + 9 =
  29. 29.13 − 9 =
  30. 30.36 + 9 =
  31. 31.54 − 9 =
  32. 32.23 − 9 =
  33. 33.47 − 9 =
  34. 34.193 − 99 =
  35. 35.189 + 99 =
  36. 36.43 + 9 =
  37. 37.60 + 19 =
  38. 38.25 + 29 =
  39. 39.402 + 99 =
  40. 40.365 − 99 =

Answer key

  1. 49
  2. 78
  3. 64
  4. 54
  5. 98
  6. 5
  7. 38
  8. 40
  9. 43
  10. 515
  11. 71
  12. 54
  13. 94
  14. 68
  15. 431
  16. 11
  17. 54
  18. 86
  19. 72
  20. 4
  21. 875
  22. 87
  23. 51
  24. 103
  25. 20
  26. 28
  27. 885
  28. 87
  29. 4
  30. 45
  31. 45
  32. 14
  33. 38
  34. 94
  35. 288
  36. 52
  37. 79
  38. 54
  39. 501
  40. 266

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