2. In a random sample of 87 college students, the average number of GroupMe messages handled in one day is 49. The 95% confidence interval for the mean number of messages handled by students
daily is given as 47 to 51.
a. What is the population standard deviation of the sample?
b. If the number of samples were doubled, by what factor would the confidence interval change
(keeping the same confidence level?)

What is the 12th term of b(n)=-4-2(n-1)

Hiroaki wants to find 3 3/4 - 7/8 explain why he must rename 3 3/4 to do the subtraction.

Kayla wants to find the width, ab, of a river. she walks along the edge of the river 65 ft and marks point c. then she walks 25 ft further and marks point d. she turns 90° and walks until her location, point a, and point c are collinear. she marks point e at this location, as shown. (a) can kayla conclude that δ and δ are similar? why or why not? (b) suppose de = 15 ft. what can kayla conclude about the width of the river?