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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 392 · 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. 1.45 + 19 =
  2. 2.70 − 9 =
  3. 3.791 + 99 =
  4. 4.28 + 29 =
  5. 5.72 − 9 =
  6. 6.30 + 19 =
  7. 7.36 + 29 =
  8. 8.498 − 99 =
  9. 9.33 + 19 =
  10. 10.26 + 9 =
  11. 11.47 + 9 =
  12. 12.68 + 19 =
  13. 13.80 + 19 =
  14. 14.22 + 9 =
  15. 15.81 − 9 =
  16. 16.28 − 9 =
  17. 17.67 − 29 =
  18. 18.19 + 9 =
  19. 19.152 − 99 =
  20. 20.84 − 19 =
  21. 21.46 + 29 =
  22. 22.32 + 9 =
  23. 23.54 − 19 =
  24. 24.57 − 29 =
  25. 25.50 + 9 =
  26. 26.62 − 9 =
  27. 27.53 − 9 =
  28. 28.669 + 99 =
  29. 29.700 − 99 =
  30. 30.413 − 99 =
  31. 31.113 + 99 =
  32. 32.47 + 29 =
  33. 33.56 − 19 =
  34. 34.39 + 9 =
  35. 35.136 + 99 =
  36. 36.110 + 99 =
  37. 37.105 − 29 =
  38. 38.72 + 19 =
  39. 39.75 − 9 =
  40. 40.666 − 99 =

Answer key

  1. 64
  2. 61
  3. 890
  4. 57
  5. 63
  6. 49
  7. 65
  8. 399
  9. 52
  10. 35
  11. 56
  12. 87
  13. 99
  14. 31
  15. 72
  16. 19
  17. 38
  18. 28
  19. 53
  20. 65
  21. 75
  22. 41
  23. 35
  24. 28
  25. 59
  26. 53
  27. 44
  28. 768
  29. 601
  30. 314
  31. 212
  32. 76
  33. 37
  34. 48
  35. 235
  36. 209
  37. 76
  38. 91
  39. 66
  40. 567

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