A flu researcher is working under the assumption that the number of people who have the flu will double each day. If two people are infected with flu the first day, after how many more days will 64 people be infected?

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Since, the flu researcher is working under the assumption that the number of people who have the flu will double each day,

Clearly, the no. of people infected each day are in Geometric Progression or G.P. with no. of people infected on the first day is 2 and total no. of people infected is 64.

So, the progression is:

2, 4, 8,.................................64

Let, the total no. of days people are infected be `n` , no. of people infected on the first day be `a` and the common ratio of the no. of people getting infected each day be `r` .

Here, a=2, r= 2 , no. of people getting infected on the nth day= 64. Then,

`a_(n)=64`

`rArr a*r^(n-1)=64`

`rArr 2*2^(n-1)=64`

`=> 2^(n-1)=32`

`=> 2^(n-1)= 2^(5)`

`=> n-1=5`

`=> n=6`

**Therefore, after (6-1) or 5 more days 64 people will be infected.**

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