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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 549 · 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. 1.78 − 9 =
  2. 2.68 + 19 =
  3. 3.31 + 29 =
  4. 4.420 − 99 =
  5. 5.18 + 29 =
  6. 6.42 − 19 =
  7. 7.222 + 99 =
  8. 8.100 − 29 =
  9. 9.64 + 9 =
  10. 10.28 + 29 =
  11. 11.51 + 29 =
  12. 12.84 − 19 =
  13. 13.27 − 9 =
  14. 14.542 + 99 =
  15. 15.77 + 29 =
  16. 16.41 − 9 =
  17. 17.23 + 19 =
  18. 18.108 − 29 =
  19. 19.85 − 29 =
  20. 20.12 + 19 =
  21. 21.64 + 19 =
  22. 22.334 − 99 =
  23. 23.322 − 99 =
  24. 24.52 + 19 =
  25. 25.213 − 99 =
  26. 26.76 + 19 =
  27. 27.35 − 29 =
  28. 28.52 − 29 =
  29. 29.129 + 99 =
  30. 30.56 + 29 =
  31. 31.14 + 9 =
  32. 32.43 − 19 =
  33. 33.27 + 29 =
  34. 34.87 − 19 =
  35. 35.39 − 29 =
  36. 36.36 − 9 =
  37. 37.68 − 29 =
  38. 38.83 − 19 =
  39. 39.69 + 29 =
  40. 40.16 + 9 =

Answer key

  1. 69
  2. 87
  3. 60
  4. 321
  5. 47
  6. 23
  7. 321
  8. 71
  9. 73
  10. 57
  11. 80
  12. 65
  13. 18
  14. 641
  15. 106
  16. 32
  17. 42
  18. 79
  19. 56
  20. 31
  21. 83
  22. 235
  23. 223
  24. 71
  25. 114
  26. 95
  27. 6
  28. 23
  29. 228
  30. 85
  31. 23
  32. 24
  33. 56
  34. 68
  35. 10
  36. 27
  37. 39
  38. 64
  39. 98
  40. 25

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