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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 937 · 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. 1.74 − 19 =
  2. 2.48 + 9 =
  3. 3.29 − 9 =
  4. 4.504 − 99 =
  5. 5.64 − 29 =
  6. 6.111 + 99 =
  7. 7.22 + 29 =
  8. 8.33 + 9 =
  9. 9.733 + 99 =
  10. 10.16 + 19 =
  11. 11.40 − 19 =
  12. 12.87 − 9 =
  13. 13.31 − 19 =
  14. 14.18 − 9 =
  15. 15.615 + 99 =
  16. 16.646 + 99 =
  17. 17.29 + 9 =
  18. 18.28 + 19 =
  19. 19.45 + 29 =
  20. 20.55 + 29 =
  21. 21.210 − 99 =
  22. 22.68 + 19 =
  23. 23.57 + 19 =
  24. 24.387 − 99 =
  25. 25.23 − 19 =
  26. 26.58 + 19 =
  27. 27.82 − 19 =
  28. 28.27 + 9 =
  29. 29.339 − 99 =
  30. 30.14 + 9 =
  31. 31.499 + 99 =
  32. 32.234 + 99 =
  33. 33.280 + 99 =
  34. 34.35 + 9 =
  35. 35.67 + 19 =
  36. 36.688 + 99 =
  37. 37.51 + 9 =
  38. 38.62 + 19 =
  39. 39.84 − 9 =
  40. 40.64 + 19 =

Answer key

  1. 55
  2. 57
  3. 20
  4. 405
  5. 35
  6. 210
  7. 51
  8. 42
  9. 832
  10. 35
  11. 21
  12. 78
  13. 12
  14. 9
  15. 714
  16. 745
  17. 38
  18. 47
  19. 74
  20. 84
  21. 111
  22. 87
  23. 76
  24. 288
  25. 4
  26. 77
  27. 63
  28. 36
  29. 240
  30. 23
  31. 598
  32. 333
  33. 379
  34. 44
  35. 86
  36. 787
  37. 60
  38. 81
  39. 75
  40. 83

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