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Math Help - plz solve this

  1. #1
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    plz solve this

    How many distinct car numbers can be formed using two letters and three digits? The two letters must be distinct and first digit should be non zero?
    468000 b] 676000 c] 608400 d] 585000


    for ex ap 539
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  2. #2
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    Quote Originally Posted by bharathlece
    How many distinct car numbers can be formed using two letters and three digits? The two letters must be distinct and first digit should be non zero?
    468000 b] 676000 c] 608400 d] 585000


    for ex ap 539
    Since there are 26 letters and the other one is different you are using for the second on 25. Now the first digit cannot be zero thus there are 9 possibilities. In the final two digits there are no restrictions thus there are 10. In total you then have,
    26(25)(9)(10)(10)=58500
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  3. #3
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    Greetings:

    PHkr's solution would be correct if the two letters and three digits were required to occupy specific positions within the five character succession, e.g., letters followed by digits, letter in first and last position with digits between. Because no such rule of order is specified, we must consider, for instance, that the letters can assume any of 5c2 different configurations (e.g., positions 1 and 2, 1 and 3, etc.). Hence the solution put forth by PHkr need only be modified by a factor of 5c2=10, putting the number of arrangements at 10(26)(25)(9)(10)(10).

    Regards,

    Rich B.
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  4. #4
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    [QUOTE=Rich B.]Greetings:

    PHkr's solution would be correct if the two letters and three digits were required to occupy specific positions within the five character succession, e.g., letters followed by digits, letter in first and last position with digits between. Because no such rule of order is specified, we must consider, for instance, that the letters can assume any of 5c2 different configurations (e.g., positions 1 and 2, 1 and 3, etc.). Hence the solution put forth by PHkr need only be modified by a factor of 5c2=10, putting the number of arrangements at 10(26)(25)(9)(10)(10).


    Which is nice, in that the proposed solution is now one of the
    options offered.

    RonL
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  5. #5
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    Indeed!

    Hi Ron:

    Indeed! In fact, it was that fact that tipped me off to take a closer look.

    Enjoy the day.

    ...Rich
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