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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 429 · 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. 1.151 − 99 =
  2. 2.29 − 19 =
  3. 3.354 − 99 =
  4. 4.295 − 99 =
  5. 5.349 − 99 =
  6. 6.43 + 29 =
  7. 7.782 − 99 =
  8. 8.63 − 9 =
  9. 9.62 − 19 =
  10. 10.35 + 29 =
  11. 11.40 − 9 =
  12. 12.40 + 29 =
  13. 13.42 − 9 =
  14. 14.43 − 9 =
  15. 15.18 + 19 =
  16. 16.378 + 99 =
  17. 17.46 + 19 =
  18. 18.61 − 29 =
  19. 19.67 + 19 =
  20. 20.68 − 19 =
  21. 21.86 − 29 =
  22. 22.138 + 99 =
  23. 23.22 + 19 =
  24. 24.79 − 19 =
  25. 25.51 − 19 =
  26. 26.328 − 99 =
  27. 27.73 + 19 =
  28. 28.35 − 19 =
  29. 29.53 + 19 =
  30. 30.31 + 19 =
  31. 31.188 + 99 =
  32. 32.29 − 9 =
  33. 33.19 − 9 =
  34. 34.23 − 9 =
  35. 35.81 − 29 =
  36. 36.48 + 19 =
  37. 37.48 − 29 =
  38. 38.31 + 29 =
  39. 39.697 − 99 =
  40. 40.41 − 19 =

Answer key

  1. 52
  2. 10
  3. 255
  4. 196
  5. 250
  6. 72
  7. 683
  8. 54
  9. 43
  10. 64
  11. 31
  12. 69
  13. 33
  14. 34
  15. 37
  16. 477
  17. 65
  18. 32
  19. 86
  20. 49
  21. 57
  22. 237
  23. 41
  24. 60
  25. 32
  26. 229
  27. 92
  28. 16
  29. 72
  30. 50
  31. 287
  32. 20
  33. 10
  34. 14
  35. 52
  36. 67
  37. 19
  38. 60
  39. 598
  40. 22

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