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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 648 · 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. 1.125 + 99 =
  2. 2.26 + 29 =
  3. 3.76 − 29 =
  4. 4.50 + 9 =
  5. 5.45 + 9 =
  6. 6.79 + 9 =
  7. 7.69 − 19 =
  8. 8.96 − 19 =
  9. 9.25 + 19 =
  10. 10.29 − 9 =
  11. 11.17 + 19 =
  12. 12.52 − 29 =
  13. 13.16 − 9 =
  14. 14.60 + 29 =
  15. 15.45 − 9 =
  16. 16.25 − 9 =
  17. 17.85 − 9 =
  18. 18.33 − 29 =
  19. 19.174 + 99 =
  20. 20.41 + 19 =
  21. 21.45 − 19 =
  22. 22.37 + 19 =
  23. 23.27 − 19 =
  24. 24.53 + 9 =
  25. 25.56 + 29 =
  26. 26.19 − 9 =
  27. 27.218 − 99 =
  28. 28.80 + 29 =
  29. 29.230 + 99 =
  30. 30.209 − 99 =
  31. 31.88 − 9 =
  32. 32.60 − 29 =
  33. 33.85 − 29 =
  34. 34.436 − 99 =
  35. 35.99 − 19 =
  36. 36.62 − 29 =
  37. 37.172 + 99 =
  38. 38.41 − 19 =
  39. 39.109 + 99 =
  40. 40.27 − 9 =

Answer key

  1. 224
  2. 55
  3. 47
  4. 59
  5. 54
  6. 88
  7. 50
  8. 77
  9. 44
  10. 20
  11. 36
  12. 23
  13. 7
  14. 89
  15. 36
  16. 16
  17. 76
  18. 4
  19. 273
  20. 60
  21. 26
  22. 56
  23. 8
  24. 62
  25. 85
  26. 10
  27. 119
  28. 109
  29. 329
  30. 110
  31. 79
  32. 31
  33. 56
  34. 337
  35. 80
  36. 33
  37. 271
  38. 22
  39. 208
  40. 18

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