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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 252 · 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. 1.53 + 19 =
  2. 2.29 + 9 =
  3. 3.810 − 99 =
  4. 4.532 + 99 =
  5. 5.80 − 9 =
  6. 6.893 − 99 =
  7. 7.45 − 9 =
  8. 8.26 − 19 =
  9. 9.88 − 29 =
  10. 10.507 + 99 =
  11. 11.50 − 29 =
  12. 12.382 − 99 =
  13. 13.52 + 19 =
  14. 14.79 + 9 =
  15. 15.486 + 99 =
  16. 16.413 − 99 =
  17. 17.63 − 29 =
  18. 18.66 − 9 =
  19. 19.43 − 29 =
  20. 20.20 + 9 =
  21. 21.28 + 9 =
  22. 22.67 + 9 =
  23. 23.36 + 9 =
  24. 24.87 − 19 =
  25. 25.73 − 9 =
  26. 26.339 − 99 =
  27. 27.40 − 19 =
  28. 28.65 + 9 =
  29. 29.78 − 29 =
  30. 30.72 + 9 =
  31. 31.23 − 9 =
  32. 32.74 + 9 =
  33. 33.107 − 29 =
  34. 34.707 − 99 =
  35. 35.40 − 29 =
  36. 36.75 + 19 =
  37. 37.764 − 99 =
  38. 38.566 + 99 =
  39. 39.55 − 19 =
  40. 40.59 − 9 =

Answer key

  1. 72
  2. 38
  3. 711
  4. 631
  5. 71
  6. 794
  7. 36
  8. 7
  9. 59
  10. 606
  11. 21
  12. 283
  13. 71
  14. 88
  15. 585
  16. 314
  17. 34
  18. 57
  19. 14
  20. 29
  21. 37
  22. 76
  23. 45
  24. 68
  25. 64
  26. 240
  27. 21
  28. 74
  29. 49
  30. 81
  31. 14
  32. 83
  33. 78
  34. 608
  35. 11
  36. 94
  37. 665
  38. 665
  39. 36
  40. 50

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