Question

What's the greatest common factor of 40, 80, 100?

Answer 1

$40|\fbox2\\20|\fbox2\\10|2\\.\ 5|\fbox5\\.\ 1|\\--------\\80|\fbox2\\40|\fbox2\\20|2\\10|2\\.\ 5|\fbox5\\.\ 1|\\--------\\100|\fbox2\\.\ 50|\fbox2\\.\ 25|\fbox5\\.\ \ 5|5\\.\ \ 1|\\===================\\GCF(40;\ 80;\ 100)=2\times2\times5=20$

Answer 2

$GCF\ is\ the\ highest\ number\ that\ divides\ those\ numbers:\\\\ 40,\ 80,\ 100\\\\ Check\ dividers\ of\ all\ numbers:\\ 40:2\\ 20:2\\ 10:2\\ 5:5\\\\ 80:2\\ 40:2\\ 20:2\\ 10:2\\ 5:5\\\\ 100:2\\ 50:2\\25:5\\5:5\\\\ GCF=2*2*5=20$