Lunch queue at school

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Amar (form captain), Brian (vice captain), Charles and Daniel are best friends in the same class at school. 

They always like to stand next to each other in the lunch queue. 

On Mondays it is a school rule that the form captain is at the front of the queue followed by the vice captain. 

There are two ways in which these boys can queue up on a Monday: ABCD and ABDC. 

On Tuesdays, the form captain must again queue up first but the remaining three boys can follow in any order. 

There are six ways in which these boys can queue up on a Tuesday. 

Four of these ways are listed below. Write down the remaining two: ABCD, ABDC, ACBD, ACDB, _______, _________ 

On Wednesdays there are no restrictions and all four boys can queue up together in any order. 

In how many ways can this be done?

Comments

  1. Anonymous12 May 2021 at 05:58

    To find the two others, you would need to notice that D is the only one that hasn't come second yet so if we put D second we get:
    1)ADBC
    2)ADCB

    ReplyDelete

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