Answer:
<u>The company should promote a lifetime of </u><u>3589 hours</u><u> for these bulbs, so that only 2% of them burnout before the claimed lifetime.</u>
Step-by-step explanation:
Consider the lifetime of light bulbs is normally distributed. Then, μ = 4000 hours and σ = 200 hours.
Let X be the lifetime of bulbs. We need to find the lifetime before which only 2% (0.02) of the bulbs burn out. Suppose the value of this lifetime is y. then, we need to find out P(X<y) = 0.02.
We will use the z-score formula:
<u>z = (x-μ)/σ</u>
P(X<y) = 0.02
P((X-μ)/σ < (y-μ)/σ) = 0.02
P(z < (y-4000)/200) = 0.02
We can find the value of z at which the probability is 0.02 from the normal distribution (areas under the normal curve) table.
From the table we can see that 0.02 lies between z values -2.05 and -2.06. So,
z = [-2.05 + (-2.06)]/2
= -4.11/2
z = -2.055
So,
(y-4000)/200 = -2.055
y-4000 = -411
y = 4000 - 411
y = 3589 hours
<u></u>
<u>The company should promote a lifetime of </u><u>3589 hours</u><u> for these bulbs, so that only 2% of them burnout before the claimed lifetime.</u>
Answer: D All of the above
Step-by-step explanation:
Addition,subtraction,multiplication and division are basic mathematical operations used in the determination and assumption of numbers.
Without them,there will be no theorems .
The horizontal distance from the base of the skyscraper out to the ship is 485.2 feet.
<h3>What is
trigonometric ratio?</h3>
Trigonometric ratio is used to show the relationship between the sides and angles of right angled triangle.
Let d represent the horizontal distance from the base of the skyscraper out to the ship. Since the angle of depression is 67°, hence:
Angle = 90 - 67 = 23°
Using trig ratio:
tan(23) = d/1143
d = 485.2 feet
The horizontal distance from the base of the skyscraper out to the ship is 485.2 feet.
Find out more on trigonometric ratio at: brainly.com/question/24349828
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