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Mathematics 7 Online
OpenStudy (anonymous):

How many 4-digit numbers can you write having 2 sets of repeated digits (eg: 2323)

OpenStudy (paxpolaris):

is 0101 an acceptable answer?

OpenStudy (paxpolaris):

Assuming 0011 or 0101 counts as a 4 digit number.... Assuming the two digits are A and B

OpenStudy (paxpolaris):

10 choices for A 9 choices for B AABB ABAB ABBA BAAB BABA BBAA 6 ways to arrange the digits.

OpenStudy (paxpolaris):

sorry.. we should restrict A to being the first digit so 3 possible ways to arrange the numbers. AABB ABAB ABBA son your answers is 10*9*3

OpenStudy (paxpolaris):

(if A can't be 0 your answer will be 9*9*3

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