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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 370 · 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. 1.32 + 19 =
  2. 2.54 + 19 =
  3. 3.34 − 29 =
  4. 4.55 + 29 =
  5. 5.41 + 19 =
  6. 6.77 + 19 =
  7. 7.61 + 29 =
  8. 8.72 + 19 =
  9. 9.200 + 99 =
  10. 10.84 − 29 =
  11. 11.22 + 9 =
  12. 12.19 + 19 =
  13. 13.467 + 99 =
  14. 14.37 + 9 =
  15. 15.50 + 9 =
  16. 16.34 + 29 =
  17. 17.78 − 9 =
  18. 18.49 + 19 =
  19. 19.46 − 29 =
  20. 20.35 − 9 =
  21. 21.53 + 29 =
  22. 22.115 + 99 =
  23. 23.298 + 99 =
  24. 24.742 − 99 =
  25. 25.22 − 19 =
  26. 26.41 + 29 =
  27. 27.91 − 29 =
  28. 28.295 + 99 =
  29. 29.53 + 19 =
  30. 30.69 − 9 =
  31. 31.542 − 99 =
  32. 32.59 − 19 =
  33. 33.48 + 19 =
  34. 34.80 − 19 =
  35. 35.622 + 99 =
  36. 36.35 + 29 =
  37. 37.29 + 9 =
  38. 38.64 + 9 =
  39. 39.43 − 19 =
  40. 40.30 − 19 =

Answer key

  1. 51
  2. 73
  3. 5
  4. 84
  5. 60
  6. 96
  7. 90
  8. 91
  9. 299
  10. 55
  11. 31
  12. 38
  13. 566
  14. 46
  15. 59
  16. 63
  17. 69
  18. 68
  19. 17
  20. 26
  21. 82
  22. 214
  23. 397
  24. 643
  25. 3
  26. 70
  27. 62
  28. 394
  29. 72
  30. 60
  31. 443
  32. 40
  33. 67
  34. 61
  35. 721
  36. 64
  37. 38
  38. 73
  39. 24
  40. 11

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