Jawabanmu

2014-04-15T20:57:18+07:00
20^2=25^2-(r1+9)^2...... 400=625-(r1+9)^2....... 225=(r1+9)^2....... 15=r1+9...... r1=15-9=6..... perbandingannya lingk1:lingk2=πr1^2:πr2^2....... 6^2:9^2...... 36:81...... 4:9