Apenny falls from a windowsill 25.0 m above the sidewalk. how fast is the penny moving when it strikes the ground? (remember that the velocity will be negative due to the downward motion of the penny)

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 =