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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 594 · 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. 1.33 − 19 =
  2. 2.16 − 9 =
  3. 3.302 − 99 =
  4. 4.64 − 29 =
  5. 5.57 + 9 =
  6. 6.68 − 9 =
  7. 7.84 − 9 =
  8. 8.131 + 99 =
  9. 9.46 − 19 =
  10. 10.69 − 19 =
  11. 11.40 − 19 =
  12. 12.29 − 9 =
  13. 13.691 + 99 =
  14. 14.63 − 29 =
  15. 15.29 + 19 =
  16. 16.35 + 29 =
  17. 17.42 + 29 =
  18. 18.14 + 9 =
  19. 19.47 − 29 =
  20. 20.69 + 29 =
  21. 21.70 + 9 =
  22. 22.54 + 9 =
  23. 23.60 + 19 =
  24. 24.259 + 99 =
  25. 25.33 − 9 =
  26. 26.99 − 29 =
  27. 27.542 + 99 =
  28. 28.33 + 9 =
  29. 29.84 − 19 =
  30. 30.41 − 29 =
  31. 31.471 − 99 =
  32. 32.307 − 99 =
  33. 33.20 + 29 =
  34. 34.63 + 9 =
  35. 35.76 − 29 =
  36. 36.71 − 29 =
  37. 37.58 − 19 =
  38. 38.38 + 9 =
  39. 39.52 − 9 =
  40. 40.51 + 29 =

Answer key

  1. 14
  2. 7
  3. 203
  4. 35
  5. 66
  6. 59
  7. 75
  8. 230
  9. 27
  10. 50
  11. 21
  12. 20
  13. 790
  14. 34
  15. 48
  16. 64
  17. 71
  18. 23
  19. 18
  20. 98
  21. 79
  22. 63
  23. 79
  24. 358
  25. 24
  26. 70
  27. 641
  28. 42
  29. 65
  30. 12
  31. 372
  32. 208
  33. 49
  34. 72
  35. 47
  36. 42
  37. 39
  38. 47
  39. 43
  40. 80

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