Answer: 4.29 kg
Explanation: If 70% of the body weight is from water, then 30% of the body weight is from non-water substances such as bones, muscles, and organs.
Let's assume the weight of the person to be x kg. Then:
70% of x kg is water weight = 0.7x kg
30% of x kg is non-water weight = 0.3x kg
Since the person has 3 liters of extracellular water in blood (vascular volume), we can convert this to kilograms using the density of water, which is 1 kg/L. Therefore:
3 liters of water = 3 kg of water
Since extracellular water is a component of the total body water, we can set up the following equation:
Total body water = Intracellular water + Extracellular water
Assuming that intracellular water is about 2/3 of the total body water and extracellular water is about 1/3 of the total body water, we can write:
Total body water = (2/3) x + (1/3) x = x
Now we can solve for x by equating the total body water to the water weight plus the non-water weight:
Total body weight = Water weight + non-water weight
x = 0.7x + 0.3x
x = 3 kg / 0.7
x = 4.29 kg
Therefore, the weight of this person is approximately 4.29 kg.