An ambulance travels down the highway at a speed of 128 km/h. Its siren emits a sound at a frequency of 925 Hz. A car traveling at 75 km/h is on the other side of the highway (it is moving in the opposite direction). The speed of sound in air is 343 m/s. (A) What is the frequency of the siren heard by a passenger in the car as the car and ambulance approach each other? (B) What is the frequency of the siren heard by a passenger in the car as the car and ambulance move away from each other?

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+15-35=-20

going in opposite directions

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 =