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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 152 · 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. 1.63 + 29 =
  2. 2.65 + 9 =
  3. 3.22 − 9 =
  4. 4.730 + 99 =
  5. 5.242 − 99 =
  6. 6.562 − 99 =
  7. 7.55 + 29 =
  8. 8.56 − 9 =
  9. 9.35 + 9 =
  10. 10.15 + 19 =
  11. 11.48 + 9 =
  12. 12.47 + 29 =
  13. 13.16 + 9 =
  14. 14.13 + 19 =
  15. 15.95 − 19 =
  16. 16.76 − 29 =
  17. 17.676 + 99 =
  18. 18.62 − 19 =
  19. 19.61 + 19 =
  20. 20.37 − 29 =
  21. 21.48 − 9 =
  22. 22.377 − 99 =
  23. 23.66 + 9 =
  24. 24.83 − 29 =
  25. 25.254 + 99 =
  26. 26.31 + 29 =
  27. 27.50 + 29 =
  28. 28.12 + 19 =
  29. 29.88 − 29 =
  30. 30.70 + 9 =
  31. 31.870 − 99 =
  32. 32.54 − 29 =
  33. 33.99 − 29 =
  34. 34.20 + 29 =
  35. 35.29 + 9 =
  36. 36.98 − 19 =
  37. 37.83 − 19 =
  38. 38.70 − 9 =
  39. 39.31 − 9 =
  40. 40.33 − 19 =

Answer key

  1. 92
  2. 74
  3. 13
  4. 829
  5. 143
  6. 463
  7. 84
  8. 47
  9. 44
  10. 34
  11. 57
  12. 76
  13. 25
  14. 32
  15. 76
  16. 47
  17. 775
  18. 43
  19. 80
  20. 8
  21. 39
  22. 278
  23. 75
  24. 54
  25. 353
  26. 60
  27. 79
  28. 31
  29. 59
  30. 79
  31. 771
  32. 25
  33. 70
  34. 49
  35. 38
  36. 79
  37. 64
  38. 61
  39. 22
  40. 14

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