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1 year ago

6

A ball is thrown downward from the top of a 120-foot building with an initial velocity of 20 feet per second. The

1 answer:

Sholpan [36]1 year ago

6 0

Answer:

$t=\frac{-5+\sqrt{505}}{8}$

Step-by-step explanation:

The ball strikes the ground when h = 0.

$-16t^2 - 20t + 120 = 0 \\ \\ 4t^2 + 5t - 30=0 \\ \\ t=\frac{-5 \pm \sqrt{5^{2}-4(4)(-30)}}{4(2)} \\ \\ t=\frac{-5 \pm \sqrt{505}}{8}$

However, as time most be positive, we only consider the positive case.

So,

$t=\frac{-5+\sqrt{505}}{8}$

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Solve for x. <br><br> −1/3x≤−6

Olin [163]

-1/3x</= -6
/-1/3 /-1/3
x</= +2
x>/=+2
The sign changes because you are dividing by a -

7 0

3 years ago

Geometry question pls help

sammy [17]

Answer:

37 degrees

Step-by-step explanation:

As XW and YZ are parallel lines, you can use the co-interior angle rule to solve for x.

This is when you see a C-shape between parallel lines. The rule states that the sum of these two co-interior angles is 180 degrees.

Therefore,

⇒ $3x - 5 + 2x = 180$

⇒ $5x - 5 = 180$ [collect like terms of x]

⇒ $5x = 185$ [add 5 to both sides]

⇒ $x = 37$ [divide both sides by 5]

Hope this helps! :D

4 0

2 years ago

A researcher wishes to estimate the percentage of adults who support abolishing the penny. What size sample should be obtained i

Scorpion4ik [409]

Answer:

a) We need a sample size of at least 3109.

b) We need a sample size of at least 4145.

Step-by-step explanation:

In a sample with a number n of people surveyed with a probability of a success of $\pi$ , and a confidence level of $1-\alpha$ , we have the following confidence interval of proportions.

$\pi \pm z\sqrt{\frac{\pi(1-\pi)}{n}}$

In which

z is the zscore that has a pvalue of $1 - \frac{\alpha}{2}$ .

The margin of error is:

$M = z\sqrt{\frac{\pi(1-\pi)}{n}}$

99% confidence level

So $\alpha = 0.01$ , z is the value of Z that has a pvalue of $1 - \frac{0.01}{2} = 0.995$ , so $Z = 2.575$ .

(a) he uses a previous estimate of 25%?

we need a sample of size at least n.

n is found when $M = 0.02, \pi = 0.25$ . So

$M = z\sqrt{\frac{\pi(1-\pi)}{n}}$

$0.02 = 2.575\sqrt{\frac{0.25*0.75}{n}}$

$0.02\sqrt{n} = 2.575\sqrt{0.25*0.75}$

$\sqrt{n} = \frac{2.575\sqrt{0.25*0.75}}{0.02}$

$(\sqrt{n})^{2} = (\frac{2.575\sqrt{0.25*0.75}}{0.02})^{2}$

$n = 3108.1$

We need a sample size of at least 3109.

(b) he does not use any prior estimates?

When we do not use any prior estimate, we use $\pi = 0.5$

So

$M = z\sqrt{\frac{\pi(1-\pi)}{n}}$

$0.02 = 2.575\sqrt{\frac{0.5*0.5}{n}}$

$0.02\sqrt{n} = 2.575\sqrt{0.5*0.5}$

$\sqrt{n} = \frac{2.575\sqrt{0.5*0.5}}{0.02}$

$(\sqrt{n})^{2} = (\frac{2.575\sqrt{0.5*0.5}}{0.02})^{2}$

$n = 4144.1$

Rounding up

We need a sample size of at least 4145.

8 0

3 years ago

Select ALL the correct answers,

Alina [70]

Answer:

7,y,6, and x are the correct answers

Step-by-step explanation:

5 0

2 years ago

At 0 seconds, mrs taylor was 10 feet off the ground. At 5 seconds, she was 20 feet off the ground. What is her rate in feet per

dexar [7]

10 feet per 5 seconds

3 0

3 years ago