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    Mymaths OW
    I can answer everything else no problem except the last one.

    A kid can't remember his dads number plate.
    plate format: XX NN XXX

    It has 2 Ds and 3 As in and the area code 07.

    Therefore it's XX 07 XXX

    How many possible number plates fit the bill?
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    (Original post by PKMN TRN JAM)
    Mymaths OW
    I can answer everything else no problem except the last one.

    A kid can't remember his dads number plate.
    plate format: XX NN XXX

    It has 2 Ds and 3 As in and the area code 07.

    Therefore it's XX 07 XXX

    How many possible number plates fit the bill?
    How many choices are there for where you can put the 2 Ds?

    Then the As go into the remaining gaps.
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    (Original post by notnek)
    How many choices are there for where you can put the 2 Ds?

    Then the As go into the remaining gaps.
    the 2 Ds can go anywhere,

    So 2!? or 5C2? then what?
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    (Original post by PKMN TRN JAM)
    the 2 Ds can go anywhere,

    So 2!? or 5C2? then what?
    2! is 2 and there are clearly more than 2 choices for the 2Ds.

    5C2 is correct.

    Now look at some examples:

    DX07DXX
    DD07XXX
    XX07DXD

    For each of these (of which there are 5C2), there is only one way of slotting in the 3 As.

    So number of possible number plates = number of ways of slotting in the 2 Ds = 5C2

    An alternative method is to consider how many choices there are for placing the 3 As. Since 5C2=5C3, this method will give you the same answer.

    Does this all make sense?
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    (Original post by notnek)
    2! is 2 and there are clearly more than 2 choices for the 2Ds.

    5C2 is correct.

    Now look at some examples:

    DX07DXX
    DD07XXX
    XX07DXD

    For each of these (of which there are 5C2), there is only one way of slotting in the 3 As.

    So number of possible number plates = number of ways of slotting in the 2 Ds = 5C2

    An alternative method is to consider how many choices there are for placing the 3 As. Since 5C2=5C3, this method will give you the same answer.

    Does this all make sense?
    Yeah I understand, thanks a bunch.

    (I would rep you but I reached my limit )
 
 
 
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