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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 841 · 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. 1.34 − 19 =
  2. 2.44 + 29 =
  3. 3.46 − 19 =
  4. 4.72 + 29 =
  5. 5.314 − 99 =
  6. 6.294 + 99 =
  7. 7.43 + 19 =
  8. 8.21 + 19 =
  9. 9.41 − 29 =
  10. 10.47 + 19 =
  11. 11.30 − 9 =
  12. 12.205 + 99 =
  13. 13.30 − 19 =
  14. 14.34 − 9 =
  15. 15.50 − 19 =
  16. 16.70 + 9 =
  17. 17.44 + 9 =
  18. 18.58 − 9 =
  19. 19.43 − 29 =
  20. 20.21 + 29 =
  21. 21.459 − 99 =
  22. 22.79 − 9 =
  23. 23.43 + 29 =
  24. 24.372 + 99 =
  25. 25.85 − 19 =
  26. 26.799 + 99 =
  27. 27.274 − 99 =
  28. 28.408 − 99 =
  29. 29.52 − 9 =
  30. 30.70 + 19 =
  31. 31.65 + 29 =
  32. 32.34 + 29 =
  33. 33.57 + 9 =
  34. 34.80 − 9 =
  35. 35.70 + 29 =
  36. 36.227 + 99 =
  37. 37.33 + 9 =
  38. 38.47 − 9 =
  39. 39.199 + 99 =
  40. 40.12 + 9 =

Answer key

  1. 15
  2. 73
  3. 27
  4. 101
  5. 215
  6. 393
  7. 62
  8. 40
  9. 12
  10. 66
  11. 21
  12. 304
  13. 11
  14. 25
  15. 31
  16. 79
  17. 53
  18. 49
  19. 14
  20. 50
  21. 360
  22. 70
  23. 72
  24. 471
  25. 66
  26. 898
  27. 175
  28. 309
  29. 43
  30. 89
  31. 94
  32. 63
  33. 66
  34. 71
  35. 99
  36. 326
  37. 42
  38. 38
  39. 298
  40. 21

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