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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 197 · 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. 1.236 + 99 =
  2. 2.29 + 19 =
  3. 3.18 + 29 =
  4. 4.72 − 19 =
  5. 5.526 − 99 =
  6. 6.94 − 29 =
  7. 7.23 + 29 =
  8. 8.47 + 9 =
  9. 9.95 − 19 =
  10. 10.15 + 29 =
  11. 11.31 − 9 =
  12. 12.588 + 99 =
  13. 13.59 − 19 =
  14. 14.94 − 19 =
  15. 15.30 + 19 =
  16. 16.51 − 19 =
  17. 17.400 + 99 =
  18. 18.544 + 99 =
  19. 19.582 + 99 =
  20. 20.12 − 9 =
  21. 21.16 + 9 =
  22. 22.37 − 9 =
  23. 23.186 − 99 =
  24. 24.38 + 19 =
  25. 25.49 + 9 =
  26. 26.52 − 9 =
  27. 27.54 − 29 =
  28. 28.70 + 9 =
  29. 29.494 − 99 =
  30. 30.39 + 29 =
  31. 31.449 + 99 =
  32. 32.61 − 19 =
  33. 33.51 + 9 =
  34. 34.543 + 99 =
  35. 35.371 − 99 =
  36. 36.384 + 99 =
  37. 37.28 + 9 =
  38. 38.46 + 29 =
  39. 39.77 + 29 =
  40. 40.48 − 9 =

Answer key

  1. 335
  2. 48
  3. 47
  4. 53
  5. 427
  6. 65
  7. 52
  8. 56
  9. 76
  10. 44
  11. 22
  12. 687
  13. 40
  14. 75
  15. 49
  16. 32
  17. 499
  18. 643
  19. 681
  20. 3
  21. 25
  22. 28
  23. 87
  24. 57
  25. 58
  26. 43
  27. 25
  28. 79
  29. 395
  30. 68
  31. 548
  32. 42
  33. 60
  34. 642
  35. 272
  36. 483
  37. 37
  38. 75
  39. 106
  40. 39

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