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.

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.

figure c

step-by-step explanation:

hope this .

answer: yard ramps with a level off platform are typically 36 feet long. truck, rather than at an angle, enabling access to those pallets at the very back of the truck. if you are using your yard ramp to convert a loading dock into a drive-in door, we even at 60 inches (5 feet) high and a 30 foot ramp, the slope of the ramp will be less

step-by-step explanation: