The stem-and-leaf plot below shows the number of pages each student in the class read the previous evening.
1 answer:
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Focus on triangles DFC and DFE:
- They are both right triangles because DF is perpendicular to EC
- DC=DE
- DF is a common side
So, the two triangles are congruent. It follows that CF=FE, and in particular
And since x=3, the length of EF is
Since 
, we know that 
follows a Poisson distribution with parameter 
.
Now assuming
denote the mean and standard deviation of , respectively, then we know right away that 
and 
.
So,
Now assuming
So,