Question

Scientists have discovered a vaccine for a debilitating disease. This year there were 570,000 reported new cases of the disease in the United States. Research indicates, that with the new vaccination, new cases will decrease by two-thirds each year.
How many new cases do you estimate in 6 years?

Answer 1

Answer: There are approximately 853827 new cases in 6 years.

Step-by-step explanation:

Since we have given that

Initial population = 570000

Rate at which population decreases is given by

$\frac{2}{3}$

Now,

First year =570000

Second year is given by

$570000\times (\frac{1}{3})$

Third year is given by

$570000(\frac{1}{3})^2$

so, there is common ratio ,

it becomes geometric progression, as there is exponential decline.

so,

$570000,570000\times \frac{1}{3},570000\times( \frac{1}{3})^2,......,570000\times (\frac{1}{3})^6$

a=570000

common ratio is given by

$r=\frac{a_2}{a_1}=\frac{1}{3}$

number of terms = 6

Sum of terms will be given by

$S_n=\frac{a(1-r^n)}{(1-r)}$

We'll put this value in this formula,

$S_6=\frac{570000(1-(\frac{1}{3})^6}{(1-\frac{1}{3})}\\\\=853827.16$

So, there are approximately 853827 new cases in 6 years.