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3 years ago

If speed varies inversely as the time it takes to drive and Kris takes 5 hours driving at 55 mph, what speed will Martin need to

Mathematics

1 answer:

galina1969 [7]3 years ago

3 0

Answer:

55mph

None of the option is correct

Step-by-step explanation:

Let v be the speed and t as the time taken. If speed varies inversely as the time it takes to drive, then v ∝ 1/t.

v = k/t where k is the constant of proportionality.

IF it takes Kris 5 hours when driving at 55 mph, then v = 55mph when t = 5 hours.

Substituting this values into the formula above;

55 = k/5

k = 55*5

k = 275mp/hr²

To calculate the speed it will Martin to drive for 5 hours, we will substitute k = 275 and t = 5 into the original equation v = k/t

v = 275/5

v = 55 mph

<em>Hence, martin will also need to drive at 55mph to take 5 hours</em>

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Answer:

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The margin of error is

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Step-by-step explanation:

Deep explanation about a confidence interval

We have that to find our $\alpha$ level, that is the subtraction of 1 by the confidence interval divided by 2. So:

$\alpha = \frac{1-0.9}{2} = 0.05$

Now, we have to find z in the Ztable as such z has a pvalue of $1-\alpha$ .

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Now, find M as such

$M = z*\frac{\sigma}{\sqrt{n}}$

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The lower end of the interval is the mean subtracted by M. So it is 6.4 - 0.3944 = 6.01 hours.

The upper end of the interval is the mean added to M. So it is 6.4 + 0.3944 = 6.74 hours.

In this problem:

The deep explanation is not that important.

We just have to recognize that the interval has a lower end and an upper end. The distance from both the upper and the lower end to the mean is M. This means that the sample mean is the halfway point between the lower end and the upper end.

The margin of error is the distance of these two points(lower and upper end) to the mean.

In our interval

Lower end: 3.23

Upper end: 3.87

Sample mean

$M = \frac{3.23 + 3.87}{2} = 3.55$

So the correct answer is:

b.3.55

The margin of error is

3.87 - 3.55 = 3.55 - 3.23 = 0.32

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