Hope you could understand.
If you have any query, feel free to ask.
Answer:
0.81
Step-by-step explanation:
Herd immunity or community immunity is the immunity seen after vaccination of a population wherein the large portion of the population becomes immune to the pathogen. It depends on vaccine efficacy and vaccination rate.
The reproduction number R_o is a factor indicating the number of people that can be infected by the person with the disease. If Ro=5 then one infected person can infect 5 people with Polio virus.
V_c= q_c/E
V_c= Vaccine coverage
q_c= herd immunity threshold
E= Vaccine efficacy= 99%=0.99

V_c= q_c/E
V_c= 0.8/0.99= 0.808= 0.81
Thus, 81% coverage or vaccination for Polio is required to stop spread of Polio in the population.
Hello,
M=middle[AB]
The triangle ABC is equilateral :
x= 15/2
Answer:
(a) A = (20mg)/(2^(t/30))
(b) 12.6mg
(c) 129.6years
Step-by-step explanation:
To calculate the amount remaining after a number of half-lives, n, we can make use of:

Where A = amount remaining
B = initial amount

(a) A = (20mg)/(2^(t/30))
(b) Mass after 20years
A = (20mg)/(2^(20/30)) ≈ 12.6mg
(c) After how long will only 1mg remain:
1mg = (20mg)/(2^(t/30))

Taking log of both sides we have:
Log(20) = (t/30)log(2)
t/30 = (log(20))/(log(2)) ≈ 4.3
t/30 = 4.3
t = 30 x 4.3 ≈ 129.6years.