How long would it take for a car to travel a distance of 350km if it is traveling at a speed of 50km/hr?

In numbers it is 4.375 hours, or 4 hours and 22.5 minutes.

Explanation:

it is a negative acceleration

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 =