15\36 = 5/12 ; 60:12=5 => 5*5/12*5=25/60
42\45 =14/15; 60:15=4 => 14*4/15*4=56/60
25\100 = 1/4 ; 60:4=15; => 1*15/4*15=15/60
9\30 = 3/10 ; 60:10=6 => 3*6/10*6=18/60
