SOLUTION: Your group are running a foundation for street children. Ms. Queen, a friend and rich benefactor, offers two options for her donations: Option A: To give $1000 on day 1, $999

Algebra ->  Average -> SOLUTION: Your group are running a foundation for street children. Ms. Queen, a friend and rich benefactor, offers two options for her donations: Option A: To give $1000 on day 1, $999      Log On


   



Question 1197953: Your group are running a foundation for street children. Ms. Queen, a friend and rich benefactor, offers two options for her donations:
Option A: To give $1000 on day 1,
$999 on day 2, $998 on day 3, with the process to end after 1000 days.
Option B: To give $1000 on the first month and increase the
donation by 12% on the next month. This will continue for 3 years
You have to tell her which option you will take.

Answer by math_tutor2020(3817) About Me  (Show Source):
You can put this solution on YOUR website!

Option A has the sequence: 1000, 999, 998, ..., 3, 2, 1

It is arithmetic with
a%5B1%5D = 1000 = first term
d = -1 = common difference
n = 1000 terms

S%5Bn%5D = sum of the first n terms of an arithmetic sequence

S%5Bn%5D+=+%28n%2F2%29%2A%282%2Aa%5B1%5D%2Bd%28n-1%29%29

S%5B1000%5D+=+%281000%2F2%29%2A%282%2A1000-1%281000-1%29%29

S%5B1000%5D+=+500500
Therefore, adding the terms 1000,999,998,...,3,2,1 will get us the sum 500500
1000+999+998+...+3+2+1 = 500500

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Option B is a geometric sequence: 1000, 1000*(1.12), 1000*(1.12)^2, ..., 1000*(1.12)^(36-1)

Note: 3 years = 3*12 = 36 months

a = 1000 = first term
r = 1.12 = common ratio, to represent an increase of 12%
n = 36 = number of terms

S%5Bn%5D = sum of the first n terms of a geometric sequence

S%5Bn%5D+=+%28a%2A%281-r%5En%29%29%2F%281-r%29

S%5B36%5D+=+%281000%2A%281-%281.12%29%5E36%29%29%2F%281-1.12%29

S%5B36%5D+=+484463.11607167

S%5B36%5D+=+484463.12

If you go for option A, then you'll get a total of $500,500.
If you go for option B, then you'll get a total of $484,463.12

We see that option A is better by 16036.88 dollars since 500500-484463.12 = 16036.88

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Answer: Option A offers the most money at $500,500.