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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 305 · 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. 1.91 − 19 =
  2. 2.38 + 29 =
  3. 3.29 + 29 =
  4. 4.57 + 19 =
  5. 5.58 + 19 =
  6. 6.604 + 99 =
  7. 7.45 + 19 =
  8. 8.48 + 29 =
  9. 9.500 + 99 =
  10. 10.51 − 19 =
  11. 11.40 + 29 =
  12. 12.14 − 9 =
  13. 13.172 − 99 =
  14. 14.80 + 19 =
  15. 15.27 − 19 =
  16. 16.98 − 19 =
  17. 17.58 + 29 =
  18. 18.54 − 19 =
  19. 19.213 − 99 =
  20. 20.565 − 99 =
  21. 21.783 − 99 =
  22. 22.800 + 99 =
  23. 23.73 − 9 =
  24. 24.81 − 29 =
  25. 25.70 + 19 =
  26. 26.15 − 9 =
  27. 27.87 − 29 =
  28. 28.100 − 29 =
  29. 29.64 − 29 =
  30. 30.44 + 29 =
  31. 31.20 + 9 =
  32. 32.634 − 99 =
  33. 33.55 + 19 =
  34. 34.56 + 29 =
  35. 35.71 − 9 =
  36. 36.36 − 19 =
  37. 37.69 − 9 =
  38. 38.41 − 9 =
  39. 39.38 + 9 =
  40. 40.16 + 19 =

Answer key

  1. 72
  2. 67
  3. 58
  4. 76
  5. 77
  6. 703
  7. 64
  8. 77
  9. 599
  10. 32
  11. 69
  12. 5
  13. 73
  14. 99
  15. 8
  16. 79
  17. 87
  18. 35
  19. 114
  20. 466
  21. 684
  22. 899
  23. 64
  24. 52
  25. 89
  26. 6
  27. 58
  28. 71
  29. 35
  30. 73
  31. 29
  32. 535
  33. 74
  34. 85
  35. 62
  36. 17
  37. 60
  38. 32
  39. 47
  40. 35

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