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3 years ago

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Blake is driving home from the water park. He drives for 60 miles and stops to rest before driving 20 more miles. Unfortunately,

Blake remembers he was supposed to pick up a present for his friend on the way home, so he turns around and drives 36 miles back towards the water park. Once he picks up the present, he drives the rest of the way home, which is 70 miles away. What is the distance from the water park to Blake's home?

1 answer:

Firlakuza [10]3 years ago

8 0

Answer:

The distance from the water park to Blake's home is 114 miles.

Step-by-step explanation:

Let's list out the steps!

1) Blake started at his home. (+0) (0)

2) Then he drove 60 miles towards his home. (+60) (60)

3) He stops and rests. (+0) (60)

4) He drives another 20 miles. (+ 20) (80)

5) He drives back, 36 miles, towards the water park. (-36) (44)

6) He drives home, which is 70 miles. (+70) (114)

The first number after each statement, is the miles added/subtracted, with each step. The second number in parenthesis, is what the total miles is, UP to that step.

Thus, from the water park, to Blake's home, it is 114 miles!

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The lifetime of a certain type of battery is normally distributed with mean value 10 hours and standard deviation 1 hour. There

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Answer:

$z=1.64$

And if we solve for a we got;

$10 +1.64*1=11.64$

So the value of height that separates the bottom 95% of data from the top 5% is 11.64

Step-by-step explanation:

Previous concepts

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".

Solution to the problem

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$X \sim N(10,1)$

Where $\mu=10$ and $\sigma=1$

For this part we want to find a value a, such that we satisfy this condition:

$P(X>a)=0.05$ (a)

$P(X$ (b)

Both conditions are equivalent on this case. We can use the z score again in order to find the value a.

As we can see on the figure attached the z value that satisfy the condition with 0.95 of the area on the left and 0.05 of the area on the right it's z=1.64. On this case P(Z<1.64)=0.95 and P(z>1.64)=0.05

If we use condition (b) from previous we have this:

$P(X$

$P(z$

But we know which value of z satisfy the previous equation so then we can do this:

$z=1.64$

And if we solve for a we got;

$10 +1.64*1=11.64$

So the value of height that separates the bottom 95% of data from the top 5% is 11.64

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3 years ago

Joey and Armando live on the same st as the park. The park is 9/10 mile from Joey's home. Joey leaves home and walks to Armando'

AleksandrR [38]

Let's start by assuming Armando's house is between Joey's and the park.

Let $x$ be the distance Joey walked to Armando's house.

<span>The park is 9/10 mile from Joey's home. Joey leaves home and walks to Armando's home. Then Joey and Armando walk 3/5 mile to the park.

</span> $\dfrac{9}{10} = x + \dfrac{3}{5}$

$x = \dfrac{9}{10} - \dfrac{3}{5} = \dfrac{9}{10} -\dfrac{6}{10} = \dfrac{3}{10}$

That's probably the answer they're looking for. But what if the park is between Joey and Armando's houses or Joey is between the park and Armando? (The latter isn't really possible with the given distances.)

Let $a, b, c$ be the distances between three collinear points like we have here. Our equation is really a few equations in one, something like

$\pm a \pm b = \pm c$

Let's get rid of the plus/minuses. Squaring,

$a^2 + b^2\pm 2ab = c^2$

$\pm 2ab = c^2-a^2-b^2$

$4a^2b^2 = (c^2-a^2-b^2)^2$

For us, that's a quadratic equation for $c^2$

$4(9/10)^2(3/5)^2= (c^2-(9/10)^2 - (3/5)^2)^2$

I'll skip right to the solutions,

$c^2=\dfrac{9}{100} \textrm{ or } c^2=\dfrac{9}{4}$

$c=\dfrac{3}{10} \textrm{ or } c=\dfrac{3}{2}$

We could have gotten the 3/2 just by adding 9/10+3/5 but this was more fun.

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