Question

The lifetime of certain kinds of electronic devices have a mean of 300 hours and standard deviation of 25 hrs . Assuming that the distribution of these lifetimes , which are measured to the nearest hour , can be approximated closely with a normal curve
A) Find the probability that any of the electronic devices will have a normal curve more than 350 hours

B) What percentage will have lifetime of 300 hours or less

C)What percentage will have lifetime from 220 to 260 hours​

Answer 1

Answer:

On a particular day 85℅ student were present in a class• If the strength of the class was 40,find the number of students absent

Answer 2

Answer:

P(X>350)= 0.02275

Step-by-step explanation:

A) Data: X= 350 or more

μ= 300

σ=25  

n= 1

Solution: Using Normal Distribution:

For less than:

P(X<350)= P ((x-μ)/σ<(350-μ)/σ)

P(X<350)= P (Z<(350-300)/25)

P(X<350)= P (Z<2)

P(X<350)= 0.97725

For more than: P(X>350)= 1-P (X<350)

P(X>350)= 1-0.97725

P(X>350)= 0.02275