Answer:
The bulbs should be replaced each 1436.9 hours.
Step-by-step explanation:
Problems of normally distributed samples are 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:

How often should the bulbs be replaced so that no more than 1% burn out between replacement periods?
This is the first percentile of hours. So it is X when Z has a pvalue of 0.01.
So it is X when Z = -2.33.




The bulbs should be replaced each 1436.9 hours.
Answer:
I don't know
Step-by-step explanation:
please mark me as the brainlist
I got 5.5 but I could for sure be wrong :/
Answer:
<h2>height = 12 cm</h2>
Step-by-step explanation:
Area of a triangle is given by

where
b is the base
h is the height
From the question
Area = 21 m²
The statement
The height of a triangle is 8 m more than the length of the base is written as
h = 8 + b
Make b the subject
That's
b = h - 8
Substitute the expression into the above formula and solve for the height
That's

Multiply through by 2
h² - 8h = 48
h² - 8h - 48 = 0
(h + 4)(h - 12) = 0
h + 4 = 0 h - 12 = 0
h = - 4 h = 12
Since the height cannot be a negative number we have the final answer as
<h3>height = 12 cm</h3>
Hope this helps you