For this your web service should return the divided values
change your code link this
for (int i = 0; i < dt.Rows.Count; i++)
{
string s=dt.Rows[i]["AdmissionNo"].ToString();
AdmissionNos.Add( Convert.ToDouble(s.Split('/')[0]) / Convert.ToDouble(s.Split('/')[1]));
}
Hope this will give you an IDEA.