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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 499 · 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. 1.757 + 99 =
  2. 2.494 + 99 =
  3. 3.56 − 9 =
  4. 4.309 − 99 =
  5. 5.539 − 99 =
  6. 6.31 + 29 =
  7. 7.57 + 19 =
  8. 8.35 − 9 =
  9. 9.76 + 9 =
  10. 10.57 + 29 =
  11. 11.176 + 99 =
  12. 12.95 − 29 =
  13. 13.46 + 19 =
  14. 14.97 − 29 =
  15. 15.44 + 9 =
  16. 16.748 − 99 =
  17. 17.41 − 9 =
  18. 18.52 − 19 =
  19. 19.643 + 99 =
  20. 20.52 − 29 =
  21. 21.24 + 9 =
  22. 22.62 − 9 =
  23. 23.73 + 19 =
  24. 24.492 − 99 =
  25. 25.64 + 9 =
  26. 26.57 + 9 =
  27. 27.512 + 99 =
  28. 28.96 − 29 =
  29. 29.174 − 99 =
  30. 30.37 + 9 =
  31. 31.46 − 9 =
  32. 32.53 − 19 =
  33. 33.38 − 29 =
  34. 34.648 + 99 =
  35. 35.75 + 29 =
  36. 36.43 − 19 =
  37. 37.301 − 99 =
  38. 38.44 − 29 =
  39. 39.55 − 29 =
  40. 40.83 − 9 =

Answer key

  1. 856
  2. 593
  3. 47
  4. 210
  5. 440
  6. 60
  7. 76
  8. 26
  9. 85
  10. 86
  11. 275
  12. 66
  13. 65
  14. 68
  15. 53
  16. 649
  17. 32
  18. 33
  19. 742
  20. 23
  21. 33
  22. 53
  23. 92
  24. 393
  25. 73
  26. 66
  27. 611
  28. 67
  29. 75
  30. 46
  31. 37
  32. 34
  33. 9
  34. 747
  35. 104
  36. 24
  37. 202
  38. 15
  39. 26
  40. 74

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