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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 44 · 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 − 9 =
  2. 2.41 + 19 =
  3. 3.43 − 29 =
  4. 4.40 + 19 =
  5. 5.62 − 29 =
  6. 6.778 + 99 =
  7. 7.69 − 9 =
  8. 8.697 + 99 =
  9. 9.59 − 9 =
  10. 10.765 + 99 =
  11. 11.14 + 19 =
  12. 12.686 + 99 =
  13. 13.33 − 19 =
  14. 14.67 + 9 =
  15. 15.77 − 29 =
  16. 16.25 − 9 =
  17. 17.575 + 99 =
  18. 18.53 + 9 =
  19. 19.68 − 9 =
  20. 20.72 + 9 =
  21. 21.87 − 29 =
  22. 22.517 + 99 =
  23. 23.76 + 19 =
  24. 24.104 − 29 =
  25. 25.47 − 9 =
  26. 26.50 − 9 =
  27. 27.42 − 9 =
  28. 28.32 + 9 =
  29. 29.56 + 9 =
  30. 30.55 + 29 =
  31. 31.86 − 9 =
  32. 32.107 + 99 =
  33. 33.77 − 9 =
  34. 34.508 + 99 =
  35. 35.69 + 29 =
  36. 36.28 − 19 =
  37. 37.19 + 9 =
  38. 38.25 + 9 =
  39. 39.19 + 29 =
  40. 40.38 + 29 =

Answer key

  1. 24
  2. 60
  3. 14
  4. 59
  5. 33
  6. 877
  7. 60
  8. 796
  9. 50
  10. 864
  11. 33
  12. 785
  13. 14
  14. 76
  15. 48
  16. 16
  17. 674
  18. 62
  19. 59
  20. 81
  21. 58
  22. 616
  23. 95
  24. 75
  25. 38
  26. 41
  27. 33
  28. 41
  29. 65
  30. 84
  31. 77
  32. 206
  33. 68
  34. 607
  35. 98
  36. 9
  37. 28
  38. 34
  39. 48
  40. 67

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