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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 987 · 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. 1.43 + 9 =
  2. 2.27 + 9 =
  3. 3.96 − 19 =
  4. 4.72 + 29 =
  5. 5.63 + 19 =
  6. 6.60 + 19 =
  7. 7.565 + 99 =
  8. 8.776 − 99 =
  9. 9.34 − 29 =
  10. 10.47 + 29 =
  11. 11.293 − 99 =
  12. 12.589 − 99 =
  13. 13.71 + 9 =
  14. 14.65 − 19 =
  15. 15.76 + 9 =
  16. 16.48 + 9 =
  17. 17.56 − 9 =
  18. 18.77 − 19 =
  19. 19.27 + 29 =
  20. 20.604 − 99 =
  21. 21.42 − 29 =
  22. 22.108 − 29 =
  23. 23.12 + 9 =
  24. 24.733 − 99 =
  25. 25.76 − 29 =
  26. 26.768 − 99 =
  27. 27.103 − 29 =
  28. 28.788 − 99 =
  29. 29.19 + 29 =
  30. 30.41 + 9 =
  31. 31.219 − 99 =
  32. 32.33 + 29 =
  33. 33.102 − 29 =
  34. 34.710 + 99 =
  35. 35.38 + 29 =
  36. 36.36 + 9 =
  37. 37.81 − 19 =
  38. 38.59 + 9 =
  39. 39.28 − 9 =
  40. 40.24 − 9 =

Answer key

  1. 52
  2. 36
  3. 77
  4. 101
  5. 82
  6. 79
  7. 664
  8. 677
  9. 5
  10. 76
  11. 194
  12. 490
  13. 80
  14. 46
  15. 85
  16. 57
  17. 47
  18. 58
  19. 56
  20. 505
  21. 13
  22. 79
  23. 21
  24. 634
  25. 47
  26. 669
  27. 74
  28. 689
  29. 48
  30. 50
  31. 120
  32. 62
  33. 73
  34. 809
  35. 67
  36. 45
  37. 62
  38. 68
  39. 19
  40. 15

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