Question

A person on the subway has a bad cold and cough into their hand and then holds onto the hand bar. This person transfers 300 virus particles to the hand bar. Half of the virus particles are destroyed every 5 minutes by air oxidation. On average, 100 people per hour during rush hour touch the same hand bar. How many people were contaminated with the cold viruses?

Answer 1

300 virus particles with the half life of 5 min
after 5 min number of particles left = 150
after 10 min number of particles = 75
after 15 min number of particles = 37.5
after 20 min number of partciles = 18.75
after 25 min number of particles = 9.375
after 30 min number of partciles = 4.6875
after 35 min number of particles = 2.34375
after 40 min number of particles = 1.1718
after 45 min number of particles = 0.586
after 50 min number of particles = 0.293
after 55 min number of particles = 0.146
after 60 min number of particles = 0.073(negligible)

after 1 hour the number of particles is negligible, so the number of people contaminated with the virus particles is nearly 100 members as 100 people per hour touch the same bar.

**If you have any questions , feel free to post in the comment section.