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Mon 23 Apr, 2007 12:26 pm
Has anybody heard of the take $50K for 30 days vs. save 1 penny (doubles after each day) for 30 days? I was just wondering what's the formula for the penny a day thing? For instance after 1st day have 1cent, after 2 days, have 3 cents (1cent + 2cent), etc.
You want the sum of a geometric series.
S=a(1-r^n)/(1-r)
Where a=1, r=2, and n=30
Hence S= (1-1073741824)/-1 ie 1073741823 cents or $10,737,418.23
I know if you don't divide by -1 you get a "-" answer. Why is it divide by -1 though? (other than that reason).
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