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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 325 · 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. 1.553 + 99 =
  2. 2.77 − 9 =
  3. 3.43 − 29 =
  4. 4.56 + 9 =
  5. 5.63 + 9 =
  6. 6.39 − 29 =
  7. 7.287 + 99 =
  8. 8.266 − 99 =
  9. 9.766 − 99 =
  10. 10.20 − 9 =
  11. 11.79 − 19 =
  12. 12.23 + 9 =
  13. 13.72 + 9 =
  14. 14.16 + 29 =
  15. 15.14 + 19 =
  16. 16.701 + 99 =
  17. 17.61 + 9 =
  18. 18.34 + 9 =
  19. 19.80 − 9 =
  20. 20.52 − 19 =
  21. 21.12 − 9 =
  22. 22.42 + 9 =
  23. 23.57 + 29 =
  24. 24.42 + 29 =
  25. 25.61 − 29 =
  26. 26.97 − 29 =
  27. 27.29 + 9 =
  28. 28.22 + 19 =
  29. 29.512 − 99 =
  30. 30.582 − 99 =
  31. 31.305 + 99 =
  32. 32.38 − 9 =
  33. 33.479 + 99 =
  34. 34.331 + 99 =
  35. 35.27 − 19 =
  36. 36.261 − 99 =
  37. 37.285 − 99 =
  38. 38.26 − 19 =
  39. 39.59 − 9 =
  40. 40.53 + 9 =

Answer key

  1. 652
  2. 68
  3. 14
  4. 65
  5. 72
  6. 10
  7. 386
  8. 167
  9. 667
  10. 11
  11. 60
  12. 32
  13. 81
  14. 45
  15. 33
  16. 800
  17. 70
  18. 43
  19. 71
  20. 33
  21. 3
  22. 51
  23. 86
  24. 71
  25. 32
  26. 68
  27. 38
  28. 41
  29. 413
  30. 483
  31. 404
  32. 29
  33. 578
  34. 430
  35. 8
  36. 162
  37. 186
  38. 7
  39. 50
  40. 62

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