Calculation of gaining ratio
X : Y : Z
Old ratio = 1/2 : 3/10 : 1/5
= 5 : 3 : 2
New ratio after Y’s retirement = 5 : 2
Gaining share = New share – Old share
X’s gain = 5/7 - 5/10 = 15/70
Z’s gain = 2/7 – 2/10 = 6/70
Gaining ratio = 15 : 6 or 5 : 2