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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 705 · 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. 1.50 − 29 =
  2. 2.112 + 99 =
  3. 3.62 + 9 =
  4. 4.75 + 19 =
  5. 5.45 + 19 =
  6. 6.177 − 99 =
  7. 7.37 + 9 =
  8. 8.29 − 19 =
  9. 9.45 + 9 =
  10. 10.28 + 29 =
  11. 11.72 + 29 =
  12. 12.64 + 19 =
  13. 13.22 + 9 =
  14. 14.67 + 19 =
  15. 15.101 − 29 =
  16. 16.34 + 19 =
  17. 17.55 − 29 =
  18. 18.12 + 19 =
  19. 19.715 + 99 =
  20. 20.26 + 19 =
  21. 21.262 − 99 =
  22. 22.39 + 19 =
  23. 23.22 + 19 =
  24. 24.75 − 19 =
  25. 25.84 − 19 =
  26. 26.92 − 29 =
  27. 27.51 − 29 =
  28. 28.14 + 19 =
  29. 29.51 + 19 =
  30. 30.503 − 99 =
  31. 31.644 + 99 =
  32. 32.512 + 99 =
  33. 33.61 + 19 =
  34. 34.15 − 9 =
  35. 35.43 + 9 =
  36. 36.52 − 9 =
  37. 37.56 + 29 =
  38. 38.23 − 9 =
  39. 39.231 − 99 =
  40. 40.26 + 9 =

Answer key

  1. 21
  2. 211
  3. 71
  4. 94
  5. 64
  6. 78
  7. 46
  8. 10
  9. 54
  10. 57
  11. 101
  12. 83
  13. 31
  14. 86
  15. 72
  16. 53
  17. 26
  18. 31
  19. 814
  20. 45
  21. 163
  22. 58
  23. 41
  24. 56
  25. 65
  26. 63
  27. 22
  28. 33
  29. 70
  30. 404
  31. 743
  32. 611
  33. 80
  34. 6
  35. 52
  36. 43
  37. 85
  38. 14
  39. 132
  40. 35

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