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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 855 · 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. 1.72 − 9 =
  2. 2.62 + 19 =
  3. 3.15 + 19 =
  4. 4.155 + 99 =
  5. 5.47 − 9 =
  6. 6.89 − 19 =
  7. 7.23 + 29 =
  8. 8.51 + 19 =
  9. 9.228 + 99 =
  10. 10.18 − 9 =
  11. 11.83 − 29 =
  12. 12.71 − 19 =
  13. 13.65 + 19 =
  14. 14.239 − 99 =
  15. 15.660 + 99 =
  16. 16.62 − 19 =
  17. 17.487 + 99 =
  18. 18.30 + 29 =
  19. 19.72 − 19 =
  20. 20.70 + 29 =
  21. 21.77 − 19 =
  22. 22.75 + 9 =
  23. 23.63 − 29 =
  24. 24.899 − 99 =
  25. 25.517 − 99 =
  26. 26.80 + 19 =
  27. 27.61 + 19 =
  28. 28.39 − 9 =
  29. 29.49 + 9 =
  30. 30.22 + 29 =
  31. 31.332 − 99 =
  32. 32.45 + 29 =
  33. 33.91 − 19 =
  34. 34.28 + 9 =
  35. 35.111 + 99 =
  36. 36.145 + 99 =
  37. 37.79 + 19 =
  38. 38.20 + 29 =
  39. 39.245 + 99 =
  40. 40.67 − 9 =

Answer key

  1. 63
  2. 81
  3. 34
  4. 254
  5. 38
  6. 70
  7. 52
  8. 70
  9. 327
  10. 9
  11. 54
  12. 52
  13. 84
  14. 140
  15. 759
  16. 43
  17. 586
  18. 59
  19. 53
  20. 99
  21. 58
  22. 84
  23. 34
  24. 800
  25. 418
  26. 99
  27. 80
  28. 30
  29. 58
  30. 51
  31. 233
  32. 74
  33. 72
  34. 37
  35. 210
  36. 244
  37. 98
  38. 49
  39. 344
  40. 58

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