In a circle with a radius of 8ft an arc is intercepted by a central angle of 135 degrees. What is the length of the arc? A: 6.28 ft
B: 9.42 ft
C: 18.84 ft
D: 28.26 ft

Greetings from Brasil...

We know that the entire length of a circle its:

C = 2πR

C = 2π8

C= 16π      circumference length

now rule of 3:

 length              º

  16π    360

     X    135

360X = 135 · 16π

X = 2160π/360

0.02% probability that the average amount billed on the sample bills is greater than $500.

Step-by-step explanation:

The Central Limit Theorem estabilishes that, for a random variable X, with mean and standard deviation , a large sample size can be approximated to a normal distribution with mean and standard deviation .

Normal probability distribution

Problems of normally distributed samples can be solved using the z-score formula.

In a set with mean and standard deviation , the zscore of a measure X is given by:

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

In this problem, we have that:

.

What is the probability that the average amount billed on the sample bills is greater than $500?

This probability is 1 subtracted by the pvalue of Z when . So

has a pvalue of 0.9998.

So there is a 1-0.9998 = 0.0002 = 0.02% probability that the average amount billed on the sample bills is greater than $500.