statistics
posted by tara .
suppose the replacement times for washing machines are normally distributed with mean 8.6 years and standard devistion of 1.6years.
a. what percentage of washing machines have replacement times less than 7 years?
b. find the probability that a washing machine will have a replacement time of more than 6.5 years?

Z = (scoremean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions related to the Z scores.
Respond to this Question
Similar Questions

Algebra
Total revenue is the total amount of money taken in by a business. An appliance firm determines that when is sells x washing machines, the total revenue, R, in dollars, is given by the polynomial R=252.05x0.5x^2 what is the total … 
algebra
total revenue is the total amount of money taken in by a business an appliance firm determines that when it sells x washing machines the total revenue, R in dollars is given by the polynomial R= 140.86x0.2x^2 what is the total revenue … 
Algebra 1
The marketing director of a department store interviewed 50 customers who had bought appliances the previous week. They found that 20% of the customers bought a washing machine and 40% bought a dishwasher. Also 48% of the customers … 
math
At Soap ans Suds there are 16 washing machines in a single row with no space between each one.Each washing mashine is 2 feet 5 inches across. What is the total length of the 16 washing machines? 
math
Q. At soap and suds there are 16 washing machines in a single row with no spa e between each one. Each washing machine is 2 feet 5 in inches across. What is the total length of the 16 washing machines. A. Do I divide 16 with 2,than … 
Grade 5 math
At soap and suds there are 16 washing machines in a single row with no space between each one.Each washing machine is 75cm across.Wht is the total length of the 16 washing machines in centimeters and meters? 
math
At soap and suds there are 16 washing machines in a single row with no space between each one.Each washing machine is 75cm across.Wht is the total length of the 16 washing machines in centimeters and meters? 
Grade 5 math
At soap and suds there are 16 washing machines in a single row with no space between each one.Each washing machine is 75cm across.Wht is the total length of the 16 washing machines in centimeters and meters? 
Math
This task is about choosing a new washing machine. Your washing machine is broken. You need a new one. The new washing machine must hold at least as much as the old one and spin at least as fast as the old one. You used your old washing … 
math
if the life in years of a washing machine is normally distributed with a mean of 15 years and a standard deviation of 1.6 years what should be the guarantee period if the company wants less than 1% of the machines to fail while under …