Y is greater than or equal to 0
Given that mean=3750 hours and standard deviation is 300:
Then:
<span>a. The probability that a lamp will last for more than 4,000 hours?
P(x>4000)=1-P(x<4000)
but
P(x<4000)=P(z<Z)
where:
z=(x-</span>μ)/σ
z=(4000-3750)/300
z=0.833333
thus
P(x<4000)=P(z<0.8333)=0.7967
thus
P(x>4000)=1-0.7967=0.2033
<span>b.What is the probability that a lamp will last less than 3,000 hours?
P(x<3000)=P(z<Z)
Z=(3000-3750)/300
z=-2.5
thus
P(x<3000)=P(z<-2.5)=0.0062
c. </span><span>.What lifetime should the manufacturer advertise for these lamps in order that only 4% of the lamps will burn out before the advertised lifetime?
the life time will be found as follows:
let the value be x
the value of z corresponding to 0.04 is z=-2.65
thus
using the formula for z-score:
-2.65=(x-3750)/300
solving for x we get:
-750=x-3750
x=-750+3750
x=3000</span>
Answer:
K=8
Step-by-step explanation:
The triangles are similar so you can set up the porpotions: 3/6=4/k then you cross multiply and solve for k
Answer:
3.33
Step-by-step explanation:
20 divided by 6 equals 3.33333333333
Round that you get 3.33
Answer:
6 feet
Step-by-step explanation:
Since there are 8 bricks and each brick is 9 inches long, that is a total of 72 inches. Now, you need to convert it from inches to feet. Since 1 foot is 12 inches, we need to divide 72 by 12 to get the number of feet. 72 / 12 is equal to 6.
