Hi Ram,
The easy way to get the total length of multiple lines is to use lisp.
Here is the code:
(defun C:TLEN (/ ss tl ent)
(setq
ss (ssget '((0 . "LINE,ARC,CIRCLE,*POLYLINE,SPLINE,ELLIPSE")))
tl 0
); end setq
(repeat (sslength ss)
(setq
ent (ssname ss 0)
tl
(+
tl
(vlax-curve-getDistAtParam ent (vlax-curve-getEndParam ent))
); end + & tl
); end setq
(ssdel ent ss)
); end repeat
(alert (strcat "Total length of selected objects is " (rtos tl)))
(princ)
); end defun
If you don't know how to use lisp, here is a link:
https://knowledge.autodesk.com/search-result/caas/CloudHelp/cloudhelp/2015/ENU/AutoCAD-AutoLISP/file...
See also screencasts below.
Thank you. 
NiCHKCiD
BIM Modeler
Technical Officer
Technical Designer
Sr. Draftsman