The table shows the ages and prices of used cars from an online site. The equation y=22-1.2x models the price as a function of age.
Age of car (in years), x 1 3 5 7 9 11 13 Price (in thousands of dollars), y 20.5 18.4 16.1 13.5 11.4 8.8 6
Describe what the slope means in terms of the situation:
8. You deposit $2800 in a savings account that earns 1% annual interest compounded semiannually. Write a function that represents the balance after t years.
9. You deposit $3800 in a savings account that earns 5% annual interest compounded quarterly. Write a function that represents the balance after t years.

There is an 84% probability that your standard refrigerator will last between 12 and 20 years.

Step-by-step explanation:

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:

A standard refrigerator's mean life expectancy is 18 years with a standard deviation of 2 years. This means that .

What is the probability that your standard refrigerator will last between 12 and 20 years?

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

X = 20

has a pvalue of 0.8413

X = 12

has a pvalue of 0.0014

This means that there is a 0.8413-0.0014 = 0.8399 = 0.84 = 84% probability that your standard refrigerator will last between 12 and 20 years.