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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 61 · 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. 1.25 + 19 =
  2. 2.72 + 9 =
  3. 3.786 − 99 =
  4. 4.17 + 9 =
  5. 5.45 + 19 =
  6. 6.15 + 9 =
  7. 7.82 − 19 =
  8. 8.73 + 19 =
  9. 9.88 − 9 =
  10. 10.190 − 99 =
  11. 11.31 − 9 =
  12. 12.322 + 99 =
  13. 13.89 − 29 =
  14. 14.79 + 9 =
  15. 15.81 − 29 =
  16. 16.62 + 29 =
  17. 17.32 − 9 =
  18. 18.517 − 99 =
  19. 19.823 − 99 =
  20. 20.45 − 19 =
  21. 21.65 + 19 =
  22. 22.69 − 9 =
  23. 23.42 + 19 =
  24. 24.51 + 9 =
  25. 25.531 + 99 =
  26. 26.88 − 19 =
  27. 27.282 + 99 =
  28. 28.354 − 99 =
  29. 29.95 − 29 =
  30. 30.830 − 99 =
  31. 31.476 + 99 =
  32. 32.77 − 9 =
  33. 33.35 − 9 =
  34. 34.47 + 19 =
  35. 35.84 − 9 =
  36. 36.22 + 19 =
  37. 37.38 − 29 =
  38. 38.30 − 9 =
  39. 39.21 + 29 =
  40. 40.21 − 9 =

Answer key

  1. 44
  2. 81
  3. 687
  4. 26
  5. 64
  6. 24
  7. 63
  8. 92
  9. 79
  10. 91
  11. 22
  12. 421
  13. 60
  14. 88
  15. 52
  16. 91
  17. 23
  18. 418
  19. 724
  20. 26
  21. 84
  22. 60
  23. 61
  24. 60
  25. 630
  26. 69
  27. 381
  28. 255
  29. 66
  30. 731
  31. 575
  32. 68
  33. 26
  34. 66
  35. 75
  36. 41
  37. 9
  38. 21
  39. 50
  40. 12

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