a.
To find: The percent of tires wear out before they reach 40,000 mi.
The percent of tires wear out before they reach 40,000 mi is 85.5%.
Given information:
Mean
Standard deviation
Calculation:
Assume the life of tire follows a
Let X be the life of tire.
Compute the value of z for
The probability is:
Thus, the percent of tires wear out before they reach 40,000 mi is 85.5%.
b.
To find: The probability a tire will wear out between 32,000 and 35,000 mi.
The probability a tire will wear out between 32,000 and 35,000 mi is 17.8%.
Calculation:
Assume the life of tire follows a normal distribution.
Let X be the life of tire.
Compute the value of z for
Compute the value of z for
The probability is:
Thus, the probability a tire will wear out between 32,000 and 35,000 mi is 17.8%.
c.
To find: The number of miles can the company guarantee these tires, if the company wants at least 90% of them to last that long.
The required life of tires is about 33,800 miles.
Calculation:
Using the calculator’s inverse Normal function, we find the 90th percentile at
This represents the life of tire that is 1.2815515 standard deviation below the mean.
The life of tires could be calculated as:
Hence, the required life of tires is about 40596 miles.
Chapter 10 Solutions
PRECALCULUS:GRAPHICAL,...-NASTA ED.
- Calculus: Early TranscendentalsCalculusISBN:9781285741550Author:James StewartPublisher:Cengage LearningThomas' Calculus (14th Edition)CalculusISBN:9780134438986Author:Joel R. Hass, Christopher E. Heil, Maurice D. WeirPublisher:PEARSONCalculus: Early Transcendentals (3rd Edition)CalculusISBN:9780134763644Author:William L. Briggs, Lyle Cochran, Bernard Gillett, Eric SchulzPublisher:PEARSON
- Calculus: Early TranscendentalsCalculusISBN:9781319050740Author:Jon Rogawski, Colin Adams, Robert FranzosaPublisher:W. H. FreemanCalculus: Early Transcendental FunctionsCalculusISBN:9781337552516Author:Ron Larson, Bruce H. EdwardsPublisher:Cengage Learning