Solution:
The following information about the chain email can be Written as follows:
1 Person Email →→6 Persons (E-mail) →6² Persons (E-mail)→6³ Persons (E-mail)+.........few Days
As you can see the number of email sent starting from person 1 to 6 persons to 36 persons to 216 persons, forms a Geometric pattern.
So, Sum of the Series = 1 + 6 + 36 + 216 + 1296 +......+ for n days
= [tex]1+6^1+6^2+6^3+6^4 +6^5 +6^6+..........+ 6^n[/tex]
Formula for n terms of a geometric series
[tex]\frac{a (r^n-1)}{r-1}[/tex]
For, Common ratio (r)≥1
Sum of above geometric series up to n terms [tex]=\frac{6^n-1}{6-1}=\frac{6^n-1}{5}[/tex]
