How do you find the weight of an object underwater

Explanation:

But Archimedes principle states that the buoyant force = weight of fluid displaced by object. From this volume you can get the mass of water displaced since the density of water is 977kg/m^3. Whatever you get multiply it by 9.8m/s^2 to covert mass to weight.

it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =

answer( sicar );