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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 946 · 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. 1.30 + 29 =
  2. 2.27 + 29 =
  3. 3.61 − 19 =
  4. 4.50 − 19 =
  5. 5.76 − 9 =
  6. 6.30 + 19 =
  7. 7.695 + 99 =
  8. 8.831 − 99 =
  9. 9.81 − 29 =
  10. 10.612 − 99 =
  11. 11.645 + 99 =
  12. 12.74 + 19 =
  13. 13.75 − 9 =
  14. 14.43 − 29 =
  15. 15.442 + 99 =
  16. 16.59 − 19 =
  17. 17.42 + 29 =
  18. 18.44 + 29 =
  19. 19.547 − 99 =
  20. 20.204 − 99 =
  21. 21.45 − 9 =
  22. 22.19 − 9 =
  23. 23.45 − 29 =
  24. 24.58 − 29 =
  25. 25.93 − 29 =
  26. 26.83 − 19 =
  27. 27.56 + 29 =
  28. 28.43 + 9 =
  29. 29.76 + 29 =
  30. 30.325 − 99 =
  31. 31.34 + 29 =
  32. 32.417 + 99 =
  33. 33.234 + 99 =
  34. 34.60 + 29 =
  35. 35.102 − 29 =
  36. 36.70 + 9 =
  37. 37.98 − 19 =
  38. 38.50 + 9 =
  39. 39.764 + 99 =
  40. 40.854 − 99 =

Answer key

  1. 59
  2. 56
  3. 42
  4. 31
  5. 67
  6. 49
  7. 794
  8. 732
  9. 52
  10. 513
  11. 744
  12. 93
  13. 66
  14. 14
  15. 541
  16. 40
  17. 71
  18. 73
  19. 448
  20. 105
  21. 36
  22. 10
  23. 16
  24. 29
  25. 64
  26. 64
  27. 85
  28. 52
  29. 105
  30. 226
  31. 63
  32. 516
  33. 333
  34. 89
  35. 73
  36. 79
  37. 79
  38. 59
  39. 863
  40. 755

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