la toate se poate aplica regula dreptunghiului:
c1= 55% --------------------> 30-20 = 10 parti sol. 55%
c.f.%= 30%
c2= 20% ------------------> 55-30 = 25 parti sol. 20%
c1= 40% --------------------> 25-15 = 10 parti sol. 40%
c.f.%= 25%
c2= 15% ------------------> 40-25 = 15 parti sol. 15%
c1= 50% --------------------> 35-25 = 10 parti sol. 50%
c.f.%= 35%
c2= 25% ------------------> 50-35 = 15 parti sol. 25%