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Katena32 [7]
3 years ago
13

While traveling to and from a certain destination, you realized increasing your speed by 30 mph saved 3 hours on your return. If

the total distance of the roundtrip was 360 miles, find the speed driven while returning.
Mathematics
1 answer:
sattari [20]3 years ago
5 0

Answer:

43.95mph

Step-by-step explanation:

let x=returning speed

x-30=foward speed

Travel time=distance/speed

180/(x-30)-180/x=3

LCD: x(x-30)

180x-180(x-30)=3x(x-3)

180x-180x+5400=3x^2-9x

3x^2-9x-5400=0

Use quadratic formula to solve

(-b+-√b^2-4ac) / 2a.

a = 3, b= -9, c = - 5400

x=[-(-9)±sqrt((-9)^2-4*3*-5400)]/2*3

x = 9±sqrt(81+64800)]/2*3

x = 9±sqrt(64881)]/6

x = 9±254.717/6

x = 263.717/6 or -254.717/6

x = 43.95 or - 42.45( will be rejected because it is less than 0)

x = 43.95

The returning speed will be 43.95mph.

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Answer: b) one tailed test.

Step-by-step explanation:

To prove that the new method of teaching economics is better than the traditional one we have make reference to mean score of students (for example) in their past exams.

Let us assume that from past exams, the mean score of students in economics exams has a value of 40.

After trying the new method in teaching, the students did economics exam and have an average of 65, this is obviously and improvement that can only be validated by performing an hypothesis test on the sample mean score.

Because the teacher is trying to prove that her method is better than the traditional, she will have to perform a one tailed test to prove that the mean score of her teaching method (65) is greater than the mean score of the traditional (40).

Due to the fact that she is opting to prove a point in just a single direction ( that her methods brings larger score compared to the traditional) a one tailed test is the perfect option.

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Four students are planning a camping trip for Labor Day weekend. They are expecting 8 additional friends to attend. Refer to the
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Find the center of mass of the wire that lies along the curve r and has density =4(1 sin4tcos4t)
dolphi86 [110]

The mass of the wire is found to be 40π√2 units.

<h3>How to find the mass?</h3>

To calculate the mass of the wire which runs along the curve r ( t ) with the density function δ=5.

The general formula is,

Mass = \int_a^b \delta\left|r^{\prime}(t)\right| d t

To find, we must differentiate this same given curve r ( t ) with respect to t to estimate |r'(t)|.

The given integration limits in this case are a = 0, b = 2π.

Now, as per the question;

The equation of the curve is given as;

r(t) = (4cost)i + (4sint)j + 4tk

Now, differentiate this same given curve r ( t ) with respect to t.

\begin{aligned}\left|r^{\prime}(t)\right| &=\sqrt{(-4 \sin t)^2+(4 \cos t)^2+4^2} \\&=\sqrt{16 \sin ^2 t+16 \cos ^2 t+16} \\&=\sqrt{16\left(\sin t^2+\cos ^2 t\right)+16}\end{aligned}

Further simplifying;

\begin{aligned}&=\sqrt{16(1)+16} \\&=\sqrt{16+16} \\&=\sqrt{32} \\\left|r^{\prime}(t)\right| &=4 \sqrt{2}\end{aligned}

Now, use integration to find the mass of the wire;

       \begin{aligned}&=\int_a^b \delta\left|r^{\prime}(t)\right| d t \\&=\int_0^{2 \pi} 54 \sqrt{2} d t \\&=20 \sqrt{2} \int_0^{2 \pi} d t \\&=20 \sqrt{2}[t]_0^{2 \pi} \\&=20 \sqrt{2}[2 \pi-0] \\&=40 \pi \sqrt{2}\end{aligned}

Therefore, the mass of the wire is estimated as 40π√2 units.

To know more about density function, here

brainly.com/question/27846146

#SPJ4

The complete question is-

Find the mass of the wire that lies along the curve r and has density δ.

r(t) = (4cost)i + (4sint)j + 4tk, 0≤t≤2π; δ=5

5 0
2 years ago
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