Mathematics, 21.01.2021 22:00, brinleychristofferse

A type of battery-operated led lights has a known mean lifetime 7.9 hours with standard deviation 0.5. Assuming that the lifetimes of these led lights have a nearly symmetric/bell-curve distribution, find the percent (%) of these led lights having lifetime between 7.9 and 8.9 hours.

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answered: diane8879

47.5% of these led lights have lifetime between 7.9 and 8.9 hours.

Step-by-step explanation:

The Empirical Rule states that, for a normally distributed random variable:

68% of the measures are within 1 standard deviation of the mean.

95% of the measures are within 2 standard deviation of the mean.

99.7% of the measures are within 3 standard deviations of the mean.

In this problem, we have that:

Mean = 7.9 hours

Standard deviation = 0.5 hours

The normal distribution is symmetric, which means that 50% of the measures are below the mean and 50% are above.

Lifetime between 7.9 and 8.9 hours:

7.9 hours is the mean.

8.9 = 7.9 + 2*0.5

So 8.9 hours is two standard deviations above the mean.

Of the 50% of the measures that are above the mean, 95% are between the mean of 7.9 and two standard deviations above the mean(8.9). So

0.5*0.95 = 0.475

47.5% of these led lights have lifetime between 7.9 and 8.9 hours.

answered: Guest

the system of inequity is

$y\leq -x+4$

$3y> x$

step-by-step explanation:

from the given graph it is noticed that we have two related lines. one is solid and another is dashed.

if a line passing through two points, then the equation of line is

$y-y_1=\frac{y_2-y_1}{x_2-x_1}(x-x_1)$

the solid line passing through the points (0,4) and (4,0).

$y-4=\frac{0-4}{4-0}(x-0)$

$y=-x+4$

the related equation of solid line is $y=-x+4$ .

similarly, find the related equation of dashed line. the dashed liune passing through the points (0,0) and (3,1).

$y-0=\frac{0-1}{3-0}(x-0)$

$3y=x$

the related equation of dashed line is $3y=x$

from the given graph it is noticed that the point (0,1) lies on the shaded region, therefore the point (0,1) must be satisfied by the related equations.

check the related equations by the point (0,1).

$1=-0+4$

$1=4$

this statement is true if the sign of inequality is < instead of equality. since it is an solid line therefore the sign of inequality will be $\leq$ . the required inequality is

$y\leq -x+4$

similarly, check the second related equation.

$3(1)=0$

it is a dashed line, so this statement is true if the sign of inequality is > . the required inequality is

$3y> x$

15 points write a system of inequalities to represent the shaded portion of the graph

answered: Guest

step-by-step explanation:

your mom

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A type of battery-operated led lights has a known mean lifetime 7.9 hours with standard deviation 0....