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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 918 · 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. 1.71 + 29 =
  2. 2.190 − 99 =
  3. 3.81 − 29 =
  4. 4.33 − 29 =
  5. 5.391 + 99 =
  6. 6.16 + 29 =
  7. 7.76 − 9 =
  8. 8.46 − 9 =
  9. 9.69 − 29 =
  10. 10.52 + 29 =
  11. 11.66 − 9 =
  12. 12.59 − 29 =
  13. 13.76 − 29 =
  14. 14.39 − 19 =
  15. 15.24 + 9 =
  16. 16.47 + 19 =
  17. 17.23 + 29 =
  18. 18.23 − 9 =
  19. 19.32 + 19 =
  20. 20.79 + 19 =
  21. 21.51 − 29 =
  22. 22.728 − 99 =
  23. 23.706 − 99 =
  24. 24.230 + 99 =
  25. 25.113 + 99 =
  26. 26.67 − 9 =
  27. 27.417 + 99 =
  28. 28.38 + 9 =
  29. 29.47 − 9 =
  30. 30.26 − 9 =
  31. 31.555 + 99 =
  32. 32.594 − 99 =
  33. 33.74 + 29 =
  34. 34.63 + 9 =
  35. 35.32 + 9 =
  36. 36.40 + 19 =
  37. 37.41 + 9 =
  38. 38.14 + 29 =
  39. 39.89 − 19 =
  40. 40.44 + 9 =

Answer key

  1. 100
  2. 91
  3. 52
  4. 4
  5. 490
  6. 45
  7. 67
  8. 37
  9. 40
  10. 81
  11. 57
  12. 30
  13. 47
  14. 20
  15. 33
  16. 66
  17. 52
  18. 14
  19. 51
  20. 98
  21. 22
  22. 629
  23. 607
  24. 329
  25. 212
  26. 58
  27. 516
  28. 47
  29. 38
  30. 17
  31. 654
  32. 495
  33. 103
  34. 72
  35. 41
  36. 59
  37. 50
  38. 43
  39. 70
  40. 53

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