Apache MPM Event MaxRequestWorkers setting

As I am new to server settings, can any one pls help me in Apache MPM Event MaxRequestWorkers settings I used following for total httpd process and avg memory ps -ylC httpd --sort:rss | awk '{sum+=$8; ++n} END {print "Tot="sum"("n")";print "Avg="sum"/"n"="sum/n/1024"MB"}'
Result is: 6 process and avg memory is 27 mb. I want to allot 4 gb for my Apache process, so how can I calculate MaxRequestWorkers Either by 4GB/27MB = 151 MaxRequestWorkers OR 4GB/27MB = 151 * 15 ThreadsPerChild =2275 MaxRequestWorkers my ThreadsPerChild=15, I believe each thread can handle 15 process is it? which one is correct setting, pls let me know