You are tuning a guitar by comparing the sound of the string with that of a standard tuning fork. you notice a beat frequency of 5 hz when both sounds are present. youfrequencyof5.youtighten the guitar string and the beat frequency rises steadily to 8 hz. to tune the string exactly to the tuning fork you shouldfork, youshould

When you tighten the string, the tension of the string increases, and this causes that the string vibrates faster (this is way the frequency increases) now, the beat frequency (or difference in the frequencies) starts at 5hz, then when you tighten the string it increases to 8hz, then you need to untighten the string in order to reach a beat frequency near to zero.

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 =