<PRE><B>Question 698535</B>
since the angles of a rhombus bisect each other and are perpendicular and meet at E you can make right angled triangle ABE 
AB=12cm, AE=5cm and BE is half BD
Using Pythagoras
AE^2 + BE^2 = AB^2
5^2 + BE^2 = 12^2
25 + BE^2 = 144
BE^2 = 144 - 25
BE^2 = 119
BE = {{{sqrt(119)}}}
BE = 10.9cm (to 1 decimal place)
BD = 21.8cm</PRE>