204
First, lookup a standard normal table and see what the z-score is for 0.025 (one half of 100% - 95%) to allow for equal sized tails. You should find that the z-score is 1.96. That means that 95% of the time, the value should be within 1.96 standard deviations of the mean. Now let's calculate the standard deviation. 800 is 800 - 1200 = -400 to the left of the mean of 1200. 1600 is 1600 - 1200 = 400 to the right of the mean of 1200. So we are an equal distance of 400 on both sides of the mean. And we know from the z-score of 1.96, that we're 1.96 standard deviations from the mean. So a little division will give us the standard deviation. Which is: 400 / 1.96 = 204.0816327
So the standard deviation of the light bulbs is 204

4 0

3 years ago

a person is standing on top of a smaller building looking across the street at a taller building, which is 260 feet away horizon

Anuta_ua [19.1K]

The height of the smaller building is 94.63 feet, computed using the trigonometric ratios.

In the question, we take AB to be the taller building, where A is its top and B is its base, CD to be the shorter building, where C is its top and D is its base, and CE to be the perpendicular from C to AB.

Given that the horizontal distance between the two buildings is 260 feet, we can say that BC = CE = 260 feet.

The angle of elevation from the top of the shorter building to the top of the taller building is 30°, that is, ∠ECA = 30°.

The angle of depression from the top of the shorter building to the base of the taller building is 20°, that is, ∠ECB = 20°.

When ∠ECB = 20°, then ∠CBD = 20°, as they are alternate angles.

We are asked to find the height of the shorter building, that is, we are asked to find CD.

In ΔCBD,

tan ∠CBD = CD/BD {perpendicular/base},

or, tan 20° = CD/260,

or, CD = 260*tan 20° = 260*0.36397023426 {∵ tan 20° = 0.36397023426},

or, CD = 94.6322609092.

Therefore, the height of the smaller building is 94.63 feet, computed using the trigonometric ratios.

Learn more about heights and distances at

brainly.com/question/2004882

#SPJ4

7 0

1 year ago

Find the surface area of the sphere with the given dimension. Leave your answer in terms of π. Sphere with radius of 60 m.

prohojiy [21]

The surface area of a sphere is given by $A=4 \pi r^{2}$ where r represents the radius.

As the radius is given as 60 meters we replace r with 60 in the formula above to get the surface area.

$A=4 \pi ( 60^{2} )=14400 \pi$

6 0

2 years ago