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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 980 · 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. 1.263 + 99 =
  2. 2.750 + 99 =
  3. 3.36 + 9 =
  4. 4.386 + 99 =
  5. 5.485 + 99 =
  6. 6.31 + 9 =
  7. 7.27 + 29 =
  8. 8.48 + 19 =
  9. 9.854 − 99 =
  10. 10.43 − 29 =
  11. 11.333 − 99 =
  12. 12.49 + 9 =
  13. 13.66 + 9 =
  14. 14.37 + 19 =
  15. 15.95 − 29 =
  16. 16.34 − 9 =
  17. 17.36 − 29 =
  18. 18.45 + 9 =
  19. 19.32 − 29 =
  20. 20.69 + 19 =
  21. 21.487 + 99 =
  22. 22.67 + 29 =
  23. 23.184 − 99 =
  24. 24.413 + 99 =
  25. 25.63 + 9 =
  26. 26.48 − 19 =
  27. 27.87 − 19 =
  28. 28.67 − 19 =
  29. 29.53 − 9 =
  30. 30.171 − 99 =
  31. 31.50 + 9 =
  32. 32.42 + 29 =
  33. 33.315 + 99 =
  34. 34.70 + 19 =
  35. 35.36 − 19 =
  36. 36.46 − 29 =
  37. 37.18 + 19 =
  38. 38.31 + 29 =
  39. 39.651 + 99 =
  40. 40.78 − 19 =

Answer key

  1. 362
  2. 849
  3. 45
  4. 485
  5. 584
  6. 40
  7. 56
  8. 67
  9. 755
  10. 14
  11. 234
  12. 58
  13. 75
  14. 56
  15. 66
  16. 25
  17. 7
  18. 54
  19. 3
  20. 88
  21. 586
  22. 96
  23. 85
  24. 512
  25. 72
  26. 29
  27. 68
  28. 48
  29. 44
  30. 72
  31. 59
  32. 71
  33. 414
  34. 89
  35. 17
  36. 17
  37. 37
  38. 60
  39. 750
  40. 59

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