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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 793 · 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. 1.24 + 9 =
  2. 2.735 − 99 =
  3. 3.24 − 9 =
  4. 4.26 + 29 =
  5. 5.40 − 29 =
  6. 6.100 − 29 =
  7. 7.72 − 9 =
  8. 8.44 − 19 =
  9. 9.62 − 19 =
  10. 10.852 − 99 =
  11. 11.33 + 9 =
  12. 12.43 + 19 =
  13. 13.34 + 19 =
  14. 14.38 + 29 =
  15. 15.48 + 29 =
  16. 16.41 − 19 =
  17. 17.829 − 99 =
  18. 18.35 − 19 =
  19. 19.683 + 99 =
  20. 20.14 + 29 =
  21. 21.57 + 19 =
  22. 22.66 − 19 =
  23. 23.36 − 29 =
  24. 24.39 + 9 =
  25. 25.73 − 9 =
  26. 26.28 − 9 =
  27. 27.629 − 99 =
  28. 28.80 − 9 =
  29. 29.762 − 99 =
  30. 30.19 + 9 =
  31. 31.18 − 9 =
  32. 32.37 − 9 =
  33. 33.791 + 99 =
  34. 34.345 − 99 =
  35. 35.23 − 19 =
  36. 36.508 + 99 =
  37. 37.27 + 19 =
  38. 38.33 + 19 =
  39. 39.99 − 19 =
  40. 40.26 − 9 =

Answer key

  1. 33
  2. 636
  3. 15
  4. 55
  5. 11
  6. 71
  7. 63
  8. 25
  9. 43
  10. 753
  11. 42
  12. 62
  13. 53
  14. 67
  15. 77
  16. 22
  17. 730
  18. 16
  19. 782
  20. 43
  21. 76
  22. 47
  23. 7
  24. 48
  25. 64
  26. 19
  27. 530
  28. 71
  29. 663
  30. 28
  31. 9
  32. 28
  33. 890
  34. 246
  35. 4
  36. 607
  37. 46
  38. 52
  39. 80
  40. 17

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