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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 682 · 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. 1.20 − 9 =
  2. 2.79 + 29 =
  3. 3.28 + 9 =
  4. 4.73 − 19 =
  5. 5.37 + 19 =
  6. 6.44 + 19 =
  7. 7.213 + 99 =
  8. 8.54 + 19 =
  9. 9.21 + 19 =
  10. 10.53 − 19 =
  11. 11.37 − 19 =
  12. 12.13 + 19 =
  13. 13.83 − 29 =
  14. 14.43 − 9 =
  15. 15.52 − 9 =
  16. 16.350 − 99 =
  17. 17.424 − 99 =
  18. 18.87 − 19 =
  19. 19.82 − 9 =
  20. 20.347 − 99 =
  21. 21.47 + 19 =
  22. 22.42 + 9 =
  23. 23.376 − 99 =
  24. 24.17 + 9 =
  25. 25.75 + 9 =
  26. 26.80 + 29 =
  27. 27.423 + 99 =
  28. 28.18 + 9 =
  29. 29.41 − 29 =
  30. 30.34 + 19 =
  31. 31.51 + 19 =
  32. 32.91 − 19 =
  33. 33.109 − 29 =
  34. 34.26 + 29 =
  35. 35.191 + 99 =
  36. 36.800 + 99 =
  37. 37.66 − 29 =
  38. 38.13 − 9 =
  39. 39.70 + 9 =
  40. 40.38 + 9 =

Answer key

  1. 11
  2. 108
  3. 37
  4. 54
  5. 56
  6. 63
  7. 312
  8. 73
  9. 40
  10. 34
  11. 18
  12. 32
  13. 54
  14. 34
  15. 43
  16. 251
  17. 325
  18. 68
  19. 73
  20. 248
  21. 66
  22. 51
  23. 277
  24. 26
  25. 84
  26. 109
  27. 522
  28. 27
  29. 12
  30. 53
  31. 70
  32. 72
  33. 80
  34. 55
  35. 290
  36. 899
  37. 37
  38. 4
  39. 79
  40. 47

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