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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 666 · 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 + 9 =
  2. 2.56 − 9 =
  3. 3.36 − 9 =
  4. 4.216 + 99 =
  5. 5.76 + 29 =
  6. 6.100 − 29 =
  7. 7.484 − 99 =
  8. 8.24 + 19 =
  9. 9.666 + 99 =
  10. 10.86 − 9 =
  11. 11.55 + 29 =
  12. 12.32 − 29 =
  13. 13.54 − 9 =
  14. 14.137 + 99 =
  15. 15.864 − 99 =
  16. 16.87 − 19 =
  17. 17.46 + 9 =
  18. 18.48 + 9 =
  19. 19.55 + 9 =
  20. 20.22 + 19 =
  21. 21.536 + 99 =
  22. 22.35 + 29 =
  23. 23.50 + 19 =
  24. 24.442 + 99 =
  25. 25.16 + 29 =
  26. 26.19 − 9 =
  27. 27.47 − 19 =
  28. 28.34 − 9 =
  29. 29.103 − 29 =
  30. 30.51 − 19 =
  31. 31.18 + 9 =
  32. 32.69 − 29 =
  33. 33.132 + 99 =
  34. 34.51 + 19 =
  35. 35.19 + 9 =
  36. 36.84 − 19 =
  37. 37.26 + 9 =
  38. 38.53 − 29 =
  39. 39.34 − 29 =
  40. 40.43 − 9 =

Answer key

  1. 43
  2. 47
  3. 27
  4. 315
  5. 105
  6. 71
  7. 385
  8. 43
  9. 765
  10. 77
  11. 84
  12. 3
  13. 45
  14. 236
  15. 765
  16. 68
  17. 55
  18. 57
  19. 64
  20. 41
  21. 635
  22. 64
  23. 69
  24. 541
  25. 45
  26. 10
  27. 28
  28. 25
  29. 74
  30. 32
  31. 27
  32. 40
  33. 231
  34. 70
  35. 28
  36. 65
  37. 35
  38. 24
  39. 5
  40. 34

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