Question: How many blood cells does an adverage 11 year old have?

Ryan Cheale answered on 13 Jun 2015:

Average 11yr old is like 35kg? which is about 4 litres of blood, 4 litres is roughly 4kg (give or take). 45% of blood is red blood cells so that gives ~2kg of blood cells. Blood cells weigh in the order of a nanogram (10^-9g = 10^-12kg) so 2/(10^-12) is about 2*10^12 or 2,000,000,000,000 which is around 2 trillion blood cells!