Using a geometric sequence, it is found that:
a) For the first 5 weeks, the numbers are: 2, 4, 8, 16, 32
b) Hence some of the volunteers can stop recruiting new volunteers during the 7th week.
<h3>What is a geometric sequence?</h3>
A geometric sequence is a sequence in which the result of the division of consecutive terms is always the same, called common ratio q.
The nth term of a geometric sequence is given by:
![a_n = a_1q^{n-1}](https://tex.z-dn.net/?f=a_n%20%3D%20a_1q%5E%7Bn-1%7D)
In which
is the first term.
For this problem, on the first week there are 2 people, and since each new people involve two more, the common ratio is of 2, hence the parameters for the geometric sequence are:
![a_1 = 2, q = 2](https://tex.z-dn.net/?f=a_1%20%3D%202%2C%20q%20%3D%202)
Hence the number of people after n weeks is:
![a_n = 2 \times 2^{n - 1}](https://tex.z-dn.net/?f=a_n%20%3D%202%20%5Ctimes%202%5E%7Bn%20-%201%7D)
For the first 5 weeks, the numbers are:
There will be 150 volunteers when
, hence:
![2 \times 2^{n - 1} = 150](https://tex.z-dn.net/?f=2%20%5Ctimes%202%5E%7Bn%20-%201%7D%20%3D%20150)
![2^{n-1} = 75](https://tex.z-dn.net/?f=2%5E%7Bn-1%7D%20%3D%2075)
![\frac{2^n}{2} = 75](https://tex.z-dn.net/?f=%5Cfrac%7B2%5En%7D%7B2%7D%20%3D%2075)
![2^n = 150](https://tex.z-dn.net/?f=2%5En%20%3D%20150)
![n = 7...](https://tex.z-dn.net/?f=n%20%3D%207...)
The above is because 2^7 = 128 and 2^8 = 256, and 128 < 150 < 256.
Hence some of the volunteers can stop recruiting new volunteers during the 7th week.
More can be learned about geometric sequences at brainly.com/question/11847927
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