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Anni [7]
3 years ago
10

A machine starts dumping sand at the rate of 35 m3/min, forming a pile in the shape of a cone. The height of the pile is always

one and one half the length of the base diameter. After 7 minutes, how fast is the radius increasing? And the height?
Mathematics
1 answer:
juin [17]3 years ago
6 0
We are given with the following given
dV/dt = 35 m3/min
h = (3/2)D

What is asked is
dr/dt at t = 7 min

The volume of a cone is
V = (1/3)πr²h

From the given
h = (3/2)D
since D = 2r
h = 3r

Subsituting
V = πr³

At t = 7 min, the volume is
V = 35(7)
V = 245
and the radius is
245 = πr³
r = 4.27

Differentiating the volume
dV/dt = 3πr² dr/dt
From the given
dV/dt = 35

Subsituting
35 = 3πr² dr/dt
So,
dr/dt = 0.20 m/s
and
dh/dt = 0.60 m/s
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Amanda made $154 for 11 hours of work. At the same rate, how many hours would she have to work to make $252?
goldenfox [79]
For this question you can say: 
154/11 = 252/?
so ? is the hours she would work:
252*11/154 = 18 hours :)))
i hope this is helpful
have a nice day 
3 0
3 years ago
What is the gradient of the line (-4, 10) to (-2, 6)<br>​
Andre45 [30]

Answer:

(2,-4)

Step-by-step explanation:

-4+2=-2

10+-4=10-4=6

6 0
2 years ago
The seventh grade class is raising money to have a class trip at the end of the year. They began the year with $1500. They now h
Nikitich [7]

Answer:

The percent of the increase for the money the class raised is 10 %

Step-by-step explanation:

Because if you divide 1500 by 10 you get 150 that means 150 is 10 % of 1500 and if you add 150 to 1500 you get 1650 so the increase of money the class raised is 10 %

I hope this helped :)

5 0
3 years ago
there are 270 at Colfax Middle School, where the ratio of boys to girls is 5:4. there are 180 students at Winthrop Middle School
ruslelena [56]

Colfax:

Add the ratio numbers together:

5 + 4 = 9

Divide total students by that:

270 / 9 = 30

Multiply each ratio by 30:

Boys = 30 *5 = 150

Girls = 30 * 4 = 120


Do the same for Winthrop:

4 +5 = 9

180 /9 = 20

Boys = 20 * 4 = 80

Girls = 20 * 5 = 100


Total students = 270 + 180 = 450

Total Girls = 120 + 100 = 220


Fraction that are girls = 220 / 450 which reduces to 22/45

4 0
3 years ago
The cosine of 23° is equivalent to the sine of what angle
Archy [21]

Answer:

So 67 degrees is one value that we can take the sine of such that is equal to cos(23 degrees).

(There are more values since we can go around the circle from 67 degrees numerous times.)

Step-by-step explanation:

You can use a co-function identity.

The co-function of sine is cosine just like the co-function of cosine is sine.

Notice that cosine is co-(sine).

Anyways co-functions have this identity:

\cos(90^\circ-x)=\sin(x)

or

\sin(90^\circ-x)=\cos(x)

You can prove those drawing a right triangle.

I drew a triangle in my picture just so I can have something to reference proving both of the identities I just wrote:

The sum of the angles is 180.

So 90+x+(missing angle)=180.

Let's solve for the missing angle.

Subtract 90 on both sides:

x+(missing angle)=90

Subtract x on both sides:

(missing angle)=90-x.

So the missing angle has measurement (90-x).

So cos(90-x)=a/c

and sin(x)=a/c.

Since cos(90-x) and sin(x) have the same value of a/c, then one can conclude that cos(90-x)=sin(x).

We can do this also for cos(x) and sin(90-x).

cos(x)=b/c

sin(90-x)=b/c

This means sin(90-x)=cos(x).

So back to the problem:

cos(23)=sin(90-23)

cos(23)=sin(67)

So 67 degrees is one value that we can take the sine of such that is equal to cos(23 degrees).

6 0
3 years ago
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