Question 1158491
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original response deleted... I'm looking at this further....<br>
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In my earlier attempt at solving this, I tried to simplify the problem by treating all the percent increases and decreases as being relative to the original price.  That way, for instance,  increases of 3% and 3% would exactly balance decreases of 1%, 2%, and 3%.<br>
However, that is probably not how the problem was intended.<br>
If the percentage increases or decreases are treated as multipliers, there is NO permutation of 5 of the 6 possible percentage changes that results in an ending price exactly equal to the starting price.<br>
So I looked at the problem again....<br>
Certainly the other tutor missed the point of the problem, finding the percent increase or decrease if each of the changes is applied once.<br>
It appears to me that a purely analytic solution would be extremely tedious, making it necessary to examine each permutation of 5 of the 6 percentage changes.<br>
So I built an excel spreadsheet with all 6^5=7776 permutations of 5 of the 6 and identified the ones that produced a product greater than 1.<br>
ANSWER: 3588 of the 7776 permutations of 5 of the 6 percentage changes produce a product greater than 1.  Therefore, the probability that the stock price will be above the original $10 after 5 days is 3588/7776, or about 46.142%.<br>
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In response to the reader's question, here is how to make the spreadsheet.<br>
The 6 numbers you are using repeatedly are 1.03, 1.02, 1.01, 0.99, 0.98, and 0.97.<br>
There will be 6^5 = 7776 rows in the table.<br>
In column A there will be 6^4=1296 entries of 1.03, followed by 1296 entries of 1.02, followed by... etc.<br>
In the first 6^4=1296 entries in column B, there will be 6^3=216 entries of 1.03, followed by 216 entries of 1.02, followed by ... etc.<br>
Then you can copy those first 1296 entries in column B 5 more times to complete column B.<br>
So you can see building the spreadsheet is not really as big a task as it seems, because you can do a huge amount of copying and pasting.<br>
Similarly, in column C, you have repeated blocks of 36 entries of 1.03, followed by 36 entries of 1.02, ... etc.<br>
And in column D the repeated pattern is blocks of 6 of each of the 6 numbers.<br>
And finally in column E the 6 numbers repeat in a cycle through the whole 7776 entries.<br>
Now the spreadsheet shows each possible permutation of 5 of the 6 possible numbers exactly once.<br>
Now in column F, make each entry the product of the entries in columns A through E of that row.  Those numbers, being the product of 5 numbers between 0.97 and 1.03, will all be close to 1.  We are of course interested in how many of them are greater than 1.<br>
To count how many of the 7776 entries in this column are greater than 1, there are 2 steps.<br>
(1) in row 1, column G, enter<br>
=IF(F1>1,1,0)<br>
Then copy that formula down through all 7776 rows of column G.<br>
That will put a 1 in column G wherever the value in column F is greater than 1 and a value of 0 wherever that value is less than 1.<br>
Then to count the number of permutations for which the product is greater than 1, simply sum the entries in column G.<br>