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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 644 · 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. 1.57 − 19 =
  2. 2.107 − 29 =
  3. 3.80 − 29 =
  4. 4.385 − 99 =
  5. 5.30 + 19 =
  6. 6.60 + 29 =
  7. 7.22 + 29 =
  8. 8.46 + 9 =
  9. 9.18 − 9 =
  10. 10.42 + 19 =
  11. 11.53 − 19 =
  12. 12.77 + 19 =
  13. 13.64 − 29 =
  14. 14.12 + 19 =
  15. 15.379 + 99 =
  16. 16.59 + 19 =
  17. 17.29 + 29 =
  18. 18.629 − 99 =
  19. 19.109 − 29 =
  20. 20.513 − 99 =
  21. 21.31 + 19 =
  22. 22.53 + 29 =
  23. 23.83 − 29 =
  24. 24.88 − 19 =
  25. 25.721 − 99 =
  26. 26.63 + 9 =
  27. 27.42 − 29 =
  28. 28.235 − 99 =
  29. 29.567 − 99 =
  30. 30.25 − 19 =
  31. 31.348 + 99 =
  32. 32.79 − 29 =
  33. 33.24 + 9 =
  34. 34.40 − 29 =
  35. 35.50 − 29 =
  36. 36.350 − 99 =
  37. 37.21 + 9 =
  38. 38.757 − 99 =
  39. 39.503 − 99 =
  40. 40.13 + 19 =

Answer key

  1. 38
  2. 78
  3. 51
  4. 286
  5. 49
  6. 89
  7. 51
  8. 55
  9. 9
  10. 61
  11. 34
  12. 96
  13. 35
  14. 31
  15. 478
  16. 78
  17. 58
  18. 530
  19. 80
  20. 414
  21. 50
  22. 82
  23. 54
  24. 69
  25. 622
  26. 72
  27. 13
  28. 136
  29. 468
  30. 6
  31. 447
  32. 50
  33. 33
  34. 11
  35. 21
  36. 251
  37. 30
  38. 658
  39. 404
  40. 32

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