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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 553 · 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. 1.76 + 29 =
  2. 2.51 + 9 =
  3. 3.36 + 29 =
  4. 4.314 − 99 =
  5. 5.71 + 29 =
  6. 6.374 + 99 =
  7. 7.75 − 9 =
  8. 8.18 + 29 =
  9. 9.26 + 29 =
  10. 10.28 + 9 =
  11. 11.28 + 19 =
  12. 12.49 + 29 =
  13. 13.413 − 99 =
  14. 14.384 − 99 =
  15. 15.32 − 19 =
  16. 16.28 + 29 =
  17. 17.51 + 29 =
  18. 18.48 + 9 =
  19. 19.137 + 99 =
  20. 20.36 + 19 =
  21. 21.26 − 9 =
  22. 22.22 + 19 =
  23. 23.34 + 19 =
  24. 24.381 + 99 =
  25. 25.641 − 99 =
  26. 26.50 + 29 =
  27. 27.58 − 19 =
  28. 28.74 − 29 =
  29. 29.507 − 99 =
  30. 30.69 − 19 =
  31. 31.55 − 9 =
  32. 32.22 + 29 =
  33. 33.506 − 99 =
  34. 34.77 + 9 =
  35. 35.75 + 29 =
  36. 36.21 + 9 =
  37. 37.45 + 29 =
  38. 38.13 − 9 =
  39. 39.534 − 99 =
  40. 40.50 − 19 =

Answer key

  1. 105
  2. 60
  3. 65
  4. 215
  5. 100
  6. 473
  7. 66
  8. 47
  9. 55
  10. 37
  11. 47
  12. 78
  13. 314
  14. 285
  15. 13
  16. 57
  17. 80
  18. 57
  19. 236
  20. 55
  21. 17
  22. 41
  23. 53
  24. 480
  25. 542
  26. 79
  27. 39
  28. 45
  29. 408
  30. 50
  31. 46
  32. 51
  33. 407
  34. 86
  35. 104
  36. 30
  37. 74
  38. 4
  39. 435
  40. 31

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