In how many different ways can the letters A, A, B, B, B, C, D, E be arranged if the letter C must be to the right of the letter D? Choose one
A) 1680	B) 2160	C) 2520	D) 3240	E) 3360
We have 8 letters out of which A appears twice and B appears three time. Total number of permutation of these letters (without restriction) would be: 8!/2!3!=3360   Now, in half of these cases D will be to the right of C and in half of these cases to the left, hence the final answer would be 3360/2= 
<gadget id="calculator">3360/2</gadget>
<output>1_680</output>
1680   1680nswer: 1680.
<result>A</result>
In how many different ways can the letters A, A, B, B, B, C, D, E be arranged if the letter C must be to the right of the letter D?