Question 300299
11, because all four sides of a rhombus have the same length by definition.




{{{drawing(400,273.6842105,-1,18,-1,12, line(0,0,11,0), line(0,0,5.943325365,9.256180833),
line(5.943325365,9.256180833,16.943325365,9.256180833),
line(11+5.943325365,9.256180833,11,0),
 locate(0,0,A), locate(11,0,B), locate(16.943325365,9.256180833,C),
locate(5.943325365,9.256180833,D), locate(5,0,11), locate(3.4,5,11)

 )}}}