Question 1142643
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An experienced teacher writes an exam so that, on average, about 5% of students will earn an A grade. 
If she has 50 students in her class and their performance is independent, what is the probability that at least one student gets an A?
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            I am writing my post with the only one goal: to explain (and to make it clear the fact) that Edwin solved, actually, 

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<U>different problem</U> than is written in the post.



The problem solved by Edwin is <U>THIS</U>:


<pre>
    The class contains 50 students. On exam, the probability that every single student will earn an A grade is 5%.

    What is the probability that at least one student gets an A ?
</pre>


My formulation is &nbsp;CRYSTALLY &nbsp;clear, &nbsp;and it is an example &nbsp;(A STANDARD, &nbsp;actually) &nbsp;on how such problems &nbsp;MUST &nbsp;BE &nbsp;FORMULATED.



The original formulation in the post is very blurred,

and I do not think that it can, in general, be solved as it is formulated.



Edwin made it absolutely correct, &nbsp;when he changed the original formulation;

but he did it without acknowledgment, &nbsp;which, &nbsp;in my view, &nbsp;is not right.



I hope &nbsp;(and I am almost sure) &nbsp;that Edwin understands it well,

but I am writing these words for the future generations of students who will read this post &nbsp;(if they do . . . ).



As it was formulated in the post originally, &nbsp;is totally different problem.



/\/\/\/\/\/\/\/


At this forum, &nbsp;I am observing last days &nbsp;<U>A &nbsp;FLOW</U>&nbsp; of problems &nbsp;VERY&nbsp; poorly and badly formulated.


My impression is that they are / were created by person having zero knowledge on &nbsp;<U>WHAT &nbsp;IS &nbsp;a &nbsp;Math &nbsp;problem</U> 

and how it should be formulated.



My hypothesis is that some former English teacher on the phone, &nbsp;without an experience in Math, 
receives formulation from the outside and dispatches them to the forum and back, making small business . . . 



It is the only way on how I can explain this flow of false Math problems arriving to the forum.



If it is so, &nbsp;then &nbsp;<U>I &nbsp;INSISTENTLY &nbsp;recommend</U> to the managers of this project to &nbsp;<U>REPLACE &nbsp;this person &nbsp;URGENTLY</U>, 

since he &nbsp;(or she) &nbsp;is not able to perform his &nbsp;(or her) &nbsp;functions properly.