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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 402 · 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. 1.48 + 19 =
  2. 2.97 − 19 =
  3. 3.60 + 9 =
  4. 4.52 + 9 =
  5. 5.52 − 19 =
  6. 6.37 − 9 =
  7. 7.50 + 9 =
  8. 8.44 − 9 =
  9. 9.791 + 99 =
  10. 10.57 + 19 =
  11. 11.58 − 29 =
  12. 12.93 − 19 =
  13. 13.48 − 9 =
  14. 14.51 − 29 =
  15. 15.34 + 9 =
  16. 16.609 + 99 =
  17. 17.43 − 19 =
  18. 18.47 + 9 =
  19. 19.234 − 99 =
  20. 20.59 − 9 =
  21. 21.75 + 19 =
  22. 22.467 − 99 =
  23. 23.64 − 29 =
  24. 24.837 − 99 =
  25. 25.21 + 19 =
  26. 26.13 + 9 =
  27. 27.38 + 19 =
  28. 28.189 + 99 =
  29. 29.856 − 99 =
  30. 30.43 − 29 =
  31. 31.14 + 19 =
  32. 32.78 − 9 =
  33. 33.61 + 9 =
  34. 34.19 + 9 =
  35. 35.86 − 9 =
  36. 36.46 + 19 =
  37. 37.59 − 19 =
  38. 38.37 − 29 =
  39. 39.22 + 29 =
  40. 40.33 + 9 =

Answer key

  1. 67
  2. 78
  3. 69
  4. 61
  5. 33
  6. 28
  7. 59
  8. 35
  9. 890
  10. 76
  11. 29
  12. 74
  13. 39
  14. 22
  15. 43
  16. 708
  17. 24
  18. 56
  19. 135
  20. 50
  21. 94
  22. 368
  23. 35
  24. 738
  25. 40
  26. 22
  27. 57
  28. 288
  29. 757
  30. 14
  31. 33
  32. 69
  33. 70
  34. 28
  35. 77
  36. 65
  37. 40
  38. 8
  39. 51
  40. 42

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