Arecent study of the lifetimes of cell phones found the average is 24.3 months. the standard deviation is 2.6 months. if a company provides its 33 employees with a cell phone, find the probability that the mean lifetime of these phones will be less than 23.8. assume cell phone life is normally distributed variable.

Answer is 0.1357

Step-by-step explanation:

Let X represent the lifetimes of cell phones.

Given that X is normal with mean = 24.3 and std dev = 2.6

Sample size = 33

Hence std error of sample = 2.6/sq rt 33

=2.6/5.74

=0.453

When x Is normal we have

(x-24.3)/0.453 ~(N(0,1)) i.e. Z variate

P(X<23.8) = P(Z<-0.5/0.453) = P(Z<-1.10)

=0.5-0.3643

=0.1357

the answer is here: : )

:

he used the algebra tiles correctly.

step-by-step explanation:

given : 3x(2x-1)

solution :

since he used algebra tiles .

armando's solution is the same in the solution shown in figure

as he distributed 2x into x and x and wrote them vertically

and also write   -1 vertically

and 3x into x and x and x and wrote it horizontally

performing the multiplication in the algebra tiles we get

and solving the given expression :

3x(2x-1)

since solving the expression using tiles   and solving the expression algebraically we get the same answer

thus   we can choose the first statement as the answer to this problem which is "he used the algebra tiles correctly".