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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 94 · 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. 1.39 + 9 =
  2. 2.41 + 29 =
  3. 3.680 − 99 =
  4. 4.24 + 19 =
  5. 5.21 + 29 =
  6. 6.319 + 99 =
  7. 7.77 + 9 =
  8. 8.51 + 29 =
  9. 9.765 − 99 =
  10. 10.45 − 29 =
  11. 11.60 + 19 =
  12. 12.278 + 99 =
  13. 13.19 + 19 =
  14. 14.54 + 19 =
  15. 15.27 − 9 =
  16. 16.14 − 9 =
  17. 17.72 + 29 =
  18. 18.74 − 29 =
  19. 19.23 + 9 =
  20. 20.259 − 99 =
  21. 21.61 + 9 =
  22. 22.73 + 9 =
  23. 23.620 + 99 =
  24. 24.24 − 9 =
  25. 25.22 + 19 =
  26. 26.72 + 19 =
  27. 27.707 − 99 =
  28. 28.34 + 29 =
  29. 29.89 − 19 =
  30. 30.71 − 29 =
  31. 31.652 + 99 =
  32. 32.37 − 9 =
  33. 33.49 − 9 =
  34. 34.32 − 29 =
  35. 35.33 − 29 =
  36. 36.38 − 29 =
  37. 37.97 − 19 =
  38. 38.34 − 29 =
  39. 39.72 − 19 =
  40. 40.98 − 19 =

Answer key

  1. 48
  2. 70
  3. 581
  4. 43
  5. 50
  6. 418
  7. 86
  8. 80
  9. 666
  10. 16
  11. 79
  12. 377
  13. 38
  14. 73
  15. 18
  16. 5
  17. 101
  18. 45
  19. 32
  20. 160
  21. 70
  22. 82
  23. 719
  24. 15
  25. 41
  26. 91
  27. 608
  28. 63
  29. 70
  30. 42
  31. 751
  32. 28
  33. 40
  34. 3
  35. 4
  36. 9
  37. 78
  38. 5
  39. 53
  40. 79

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