Question 331634
I assume that D and d are the same (ie not distinguishable because of capitalization)

there are 6 letters and these letters can be arranged in 6! different ways

6!=720

but...... there are 2 "d"s and 2 "o"s which are indistinguishable 
some of these arrangements will be the same  and wil need to be accounted for
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So the answer is 6!/(2!*2!) = 180 different arrangements.