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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 773 · 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. 1.72 − 29 =
  2. 2.701 + 99 =
  3. 3.52 + 29 =
  4. 4.98 − 29 =
  5. 5.28 + 19 =
  6. 6.21 − 9 =
  7. 7.52 − 9 =
  8. 8.37 + 19 =
  9. 9.32 + 9 =
  10. 10.33 − 9 =
  11. 11.42 + 19 =
  12. 12.83 − 29 =
  13. 13.21 + 9 =
  14. 14.235 + 99 =
  15. 15.54 + 29 =
  16. 16.458 − 99 =
  17. 17.44 + 9 =
  18. 18.376 − 99 =
  19. 19.522 + 99 =
  20. 20.47 + 19 =
  21. 21.281 − 99 =
  22. 22.33 + 9 =
  23. 23.30 − 9 =
  24. 24.51 + 9 =
  25. 25.411 + 99 =
  26. 26.13 + 19 =
  27. 27.30 + 19 =
  28. 28.62 − 19 =
  29. 29.39 + 9 =
  30. 30.76 + 19 =
  31. 31.52 + 9 =
  32. 32.17 + 9 =
  33. 33.675 − 99 =
  34. 34.404 + 99 =
  35. 35.564 − 99 =
  36. 36.58 − 9 =
  37. 37.29 − 19 =
  38. 38.54 − 29 =
  39. 39.33 + 19 =
  40. 40.50 + 19 =

Answer key

  1. 43
  2. 800
  3. 81
  4. 69
  5. 47
  6. 12
  7. 43
  8. 56
  9. 41
  10. 24
  11. 61
  12. 54
  13. 30
  14. 334
  15. 83
  16. 359
  17. 53
  18. 277
  19. 621
  20. 66
  21. 182
  22. 42
  23. 21
  24. 60
  25. 510
  26. 32
  27. 49
  28. 43
  29. 48
  30. 95
  31. 61
  32. 26
  33. 576
  34. 503
  35. 465
  36. 49
  37. 10
  38. 25
  39. 52
  40. 69

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