The amount of blood in an adult human is relatively constant: Around 4.7 litres, with of total weight of ~4.4 Kg (average density of blood: ~1.06). Perhaps slightly more (~5 litres?). And slightly less in women. So the percentage of total body weight varies, depending of total body weight. More information and details here: Volume of Blood in a Human
Social issue. A social issue is a problem that influences a considerable number of the individuals within a society. It is often the consequence of factors extending beyond an individual's social issue is the source of a conflicting opinion on the grounds of what is perceived as a morally just personal life or societal order. Social issues are distinguished from economic issues; however, some issues have both social and economic aspects. There are also issues that don't fall into either category, such as warf
What is a social problem? A social problem is a condition that at least some people in a community view as being undesirable. Everyone would agree about some social problems, such as murders and DWI traffic deaths. Other social problems may be viewed as such by certain groups of people. Teenagers who play loud music in a public park obviously do not view it as a problem, but some other people may consider it an undesirable social condition.