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A new computer virus attacks a folder consisting of 200 files. Each gets damaged with probability $0.2$ independently of other files. What is the probability that fewer than $50$ files get damaged?

I need help for this question. Does anyone please can provide the answer for me as step-by-step?

Sorry and thank you :(

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    What have you tried so far? This website is here to help you if you get stuck on something but it's not supposed to be a place where people solve your homework for you. If you tell us what you've tried, we might be able to point you in the right direction. – 2017-02-04

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Step 1. $X \sim \mathsf{Binom}(n = 200, p =.2)$ counts damaged files.

Step 2. You seek $P(X < 50) = P(X \le 49).$

Step 3. Find the numerical value of probability in Step 2. Perhaps you are supposed to use a normal approximation and perhaps to use software for an exact answer. You have provided no context, so I can't say which.

Notes: (1) The average number of files damaged is $\mu = np = 40$ and $\sigma = \sqrt{np(1-p)} \approx 5.66,$ so you might guess the probability is considerably more than 1/2. (2) Using software, I get $P(X < 50) \approx .95,$ I hope you can finish this problem with this start.