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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 347 · 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. 1.37 + 9 =
  2. 2.50 + 29 =
  3. 3.62 − 19 =
  4. 4.183 − 99 =
  5. 5.60 + 29 =
  6. 6.64 + 19 =
  7. 7.16 − 9 =
  8. 8.40 + 9 =
  9. 9.73 − 9 =
  10. 10.80 + 29 =
  11. 11.53 + 29 =
  12. 12.167 + 99 =
  13. 13.749 − 99 =
  14. 14.14 − 9 =
  15. 15.43 + 19 =
  16. 16.12 + 29 =
  17. 17.732 + 99 =
  18. 18.36 − 9 =
  19. 19.19 + 19 =
  20. 20.24 − 9 =
  21. 21.28 + 29 =
  22. 22.26 + 9 =
  23. 23.504 + 99 =
  24. 24.51 + 29 =
  25. 25.25 + 29 =
  26. 26.53 − 19 =
  27. 27.24 + 9 =
  28. 28.42 + 9 =
  29. 29.52 − 19 =
  30. 30.79 − 29 =
  31. 31.28 + 19 =
  32. 32.12 − 9 =
  33. 33.80 + 9 =
  34. 34.25 − 9 =
  35. 35.278 + 99 =
  36. 36.38 + 29 =
  37. 37.28 − 9 =
  38. 38.235 − 99 =
  39. 39.352 + 99 =
  40. 40.196 + 99 =

Answer key

  1. 46
  2. 79
  3. 43
  4. 84
  5. 89
  6. 83
  7. 7
  8. 49
  9. 64
  10. 109
  11. 82
  12. 266
  13. 650
  14. 5
  15. 62
  16. 41
  17. 831
  18. 27
  19. 38
  20. 15
  21. 57
  22. 35
  23. 603
  24. 80
  25. 54
  26. 34
  27. 33
  28. 51
  29. 33
  30. 50
  31. 47
  32. 3
  33. 89
  34. 16
  35. 377
  36. 67
  37. 19
  38. 136
  39. 451
  40. 295

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