2/3×5/6×27/40= 1/3×30/31×1/5=
2/3 * 5/6 * 27/40 = (2*5*27) / (3*6*40) = 3/8 1/30 * 30/31 * 1/5 = (1*30*1) / (30*31*5) = 1/155