Algebra.Com's Answer #674401 by ikleyn(52803)![\"\"](\"/images/stars/stars-13.gif\")  
You can put this solution on YOUR website!
.
\n" );
document.write( "In  MNK, MS and NR are medians. If MS = 15, NR = 18, and MN = 21, what is the perimeter of PRS
\n" );
document.write( "(P is the point of concurrency) and why?
\n" );
document.write( "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\r
\n" );
document.write( "
\n" );
document.write( "\n" );
document.write( "\r\n" );
document.write( "In triangle PRS the side RS is the mid-segment of the triangle MNK.\r\n" );
document.write( "\r\n" );
document.write( "The length |RS| is half of the length MN: |RS| =  *|MN| =  = 10.5 units.\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "The side PR of the triangle PRS has the length of (1/3) of the length of the median NR: |PR| =  *|NR| =  = 6 units.\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "The side PS of the triangle PRS has the length of (1/3) of the length of the median MS: |PS| = *|MS|}}} =  = 5 units.\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "Now, the perimeter of the triangle PRS is |RS| + |PR| + |PS| = 10.5 + 6 + 5 = 21.5 units.\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "We used the fact that in any triangle the concurrency point of medians divides each median in the ratio 2:1 counting from the vertex to the base.\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "See the lesson Medians of a triangle are concurrent in this site.\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "Answer. The perimeter of the triangle PRS is 21.5 units.\r\n" );
document.write( " \r
\n" );
document.write( "\n" );
document.write( "Also, you have this free of charge online textbook on Geometry\r
\n" );
document.write( "\n" );
document.write( " GEOMETRY - YOUR ONLINE TEXTBOOK \r
\n" );
document.write( "\n" );
document.write( "in this site.\r
\n" );
document.write( "
\n" );
document.write( "\n" );
document.write( "The referred lesson is the part of this online textbook under the topic \"Properties of triangles\". \r
\n" );
document.write( "
\n" );
document.write( "\n" );
document.write( " \n" );
document.write( " |