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2 years ago

-3a + 12b=24 -a+9b=6

1 answer:

6 0

Antti entered a -kilometer race. His goal is to finish in one hour. He starts off sprinting, and completes the first kilometers of the race at an average speed of kilometers per hour.

To achieve his goal of a one-hour finish time, what average speed (in kilometers per hour) must Antti maintain for the last kilometers of the race?

Enter your answer as a number in decimal form, without units.Hint(s):

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The surface area of a melting snowball decreases at a rate of3.8cm2/min. Find the rate at which its diameter decreases when the

Scorpion4ik [409]

Answer:

Step-by-step explanation:

This is a pretty basic related rates problem. I'm going to go through this just like I do in class when I'm teaching it to my students.

We see we have a snowball, which is a sphere. We are talking about the surface area of this sphere which has a formula of

$S=4\pi r^2$

In the problem we are given diameter, not radius. What we know about the relationship between a radius and a diameter is that

d = 2r so

$\frac{d}{2}=r$ Now we can have the equation in terms of diameter instead of radius. Rewriting:

$S=4\pi(\frac{d}{2})^2$ which simplifies to

$S=4\pi(\frac{d^2}{4})$ and a bit more to

$S=\pi d^2$ (the 4's cancel out by division). Now that is a simple equation for which we have to find the derivative with respect to time.

$\frac{dS}{dt}=\pi*2d\frac{dD}{dt}$ Now let's look at the problem and see what we are given as far as information.

The rate at which the surface area changes is -3.8, and we are looking for $\frac{dD}{dt}$ , the rate at which the diameter is changing, when the diameter is 13. Filling in:

$-3.8=\pi(2)(13)\frac{dD}{dt}$ and solving for the rate at which the diameter is changing:

$-\frac{3.8}{26\pi}=\frac{dD}{dt}$ and divide to get

$\frac{dD}{dt}=-.459\frac{cm}{min}$ Obviously, the negative means that the diameter is decreasing.

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3 years ago

What is the correct definition for tan 0

Reptile [31]

$tan\theta=\frac{sin\theta}{cos\theta}\\\\\\Look\ at\ the\ picture.\\\\In\ a\ right\ triangle:\\\\sin\theta=\frac{a}{c};\ cos\theta=\frac{b}{c};\ tan\theta=\frac{a}{b}\\\\\frac{sin\theta}{cos\theta}=\frac{\frac{a}{c}}{\frac{b}{c}}=\frac{a}{c}\times\frac{c}{b}=\frac{a}{b}=tan\theta$

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3 years ago

Why is it important to reduce radicals

OleMash [197]

Simplifying radical expressions expression is important before addition or subtraction because it you need to which like terms can be added or subtracted. If we hadn't simplified the radical expressions, we would not have come to this solution. In a way, this is similar to what would be done for polynomial expression.

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2 years ago

Which values of k are solutions to the inequality StartAbsoluteValue negative k minus 2 EndAbsoluteValue less-than 18? Check all

Stella [2.4K]

Answer:

You could just replace all the given possible values of k in the inequality and see which ones are solutions, but let's solve this in a more interesting way:

First, remember how the absolute value works:

IxI = x if x ≥ 0

IxI = -x if x ≤ 0

Then if we have something like:

IxI < B

We can rewrite this as

-B < x < B

Now let's answer the question, here we have the inequality:

I-k -2I < 18

Then we can rewrite this as:

-18 < (-k - 2) < 18

Now let's isolate k:

first, we can add 2 in the 3 parts of the inequality:

-18 + 2 < -k - 2 + 2 < 18 + 2

-16 < -k < 20

Now we can multiply all sides by -1, remember that this also changes the direction of the signs, then:

-1*-16 > -1*-k > -1*20

16 > k > -20

Then k can be any value between these two limits.

So the correct options (from the given ones) are:

k = -16

k = -8

k = 0

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2 years ago

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Describe the locus in space.

yanalaym [24]

Answer: an endless cylinder with radius 4 mm and centerline

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3 years ago