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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 809 · 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. 1.69 + 19 =
  2. 2.52 + 9 =
  3. 3.28 − 19 =
  4. 4.56 + 19 =
  5. 5.48 − 9 =
  6. 6.72 − 9 =
  7. 7.16 + 29 =
  8. 8.26 − 19 =
  9. 9.55 − 19 =
  10. 10.441 + 99 =
  11. 11.27 − 9 =
  12. 12.73 + 9 =
  13. 13.57 + 29 =
  14. 14.52 + 19 =
  15. 15.832 − 99 =
  16. 16.439 + 99 =
  17. 17.46 − 29 =
  18. 18.28 + 29 =
  19. 19.40 − 9 =
  20. 20.51 − 9 =
  21. 21.315 + 99 =
  22. 22.41 − 9 =
  23. 23.78 − 29 =
  24. 24.103 − 29 =
  25. 25.59 − 9 =
  26. 26.62 − 29 =
  27. 27.32 − 9 =
  28. 28.29 − 19 =
  29. 29.49 + 9 =
  30. 30.27 + 19 =
  31. 31.72 − 19 =
  32. 32.29 + 9 =
  33. 33.30 − 9 =
  34. 34.65 + 29 =
  35. 35.14 + 19 =
  36. 36.51 − 29 =
  37. 37.93 − 19 =
  38. 38.43 + 9 =
  39. 39.57 − 9 =
  40. 40.436 + 99 =

Answer key

  1. 88
  2. 61
  3. 9
  4. 75
  5. 39
  6. 63
  7. 45
  8. 7
  9. 36
  10. 540
  11. 18
  12. 82
  13. 86
  14. 71
  15. 733
  16. 538
  17. 17
  18. 57
  19. 31
  20. 42
  21. 414
  22. 32
  23. 49
  24. 74
  25. 50
  26. 33
  27. 23
  28. 10
  29. 58
  30. 46
  31. 53
  32. 38
  33. 21
  34. 94
  35. 33
  36. 22
  37. 74
  38. 52
  39. 48
  40. 535

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