A computer virus infects an e-mail account and sends itself to 4 new accounts. The next day, each of those accounts sends the virus to 4 other accounts, and so on. How many accounts are infected with the virus after five days?

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Answer 1 · 2017-10-12T12:14:38

After #5# days total infected accounts are #1365# in number.

Virus infects in geometrical progression of which #1#st term is

#a_1=4 # , common ratio is #r=4#, number of terms is #4#

G.P sum formula is #S_n = a_1* (r^n-1)/(r-1) :. #

#S_5 = 4* (4^5-1)/(4-1)=4*1023/3 = 1364# Taking the initial

#1# , total infected accounts are #1364+1=1365# in number.

After #5# days total infected accounts are #1365# in number.[Ans]