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fredd [130]
4 years ago
8

A cylindrical metal pipe has a diameter of 20 millimeters and a height of 21 millimeters. A cylindrical hole cut out of the cent

er has a radius of 6 millimeters.
Which expressions represent the volume of metal needed, in cubic millimeters, to make the pipe? Check all that apply.

21π(10)2 – 21π(6)2
π(20)2(21) – π(6)2
2,100π – 756π
7,644π
1,344

Answer is choice 1 and 3.

Mathematics
2 answers:
salantis [7]4 years ago
7 0
1 and 3 (a and c) are both correct
qaws [65]4 years ago
6 0
The first and third options are correct
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A moving sidewalk at an airport glides a rate of 1.8 feet per second. Walking on the moving sidewalk, you travel 100 feet forwar
uranmaximum [27]

Answer: The walking speed is 4.2 feet per second.

Step-by-step explanation:

If your walking speed is S, then we can use the relation:

Time = distance/speed.

in the moving sidewalk the speed is S + 1.8ft/s.

moving forward:

speed = S + 1.8ft/s

Distance = 100 feet

Time = T

T = 100ft/(S + 1.8ft/s)

moving in the opposite direction (now the velocity of the moving sidewalk must be subtracted)

speed = S - 1.8ft/s

distance = 40 feet

time = T

T = 40ft/(S - 1.8ft/s)

Then we have two equations:

T = 100ft/(S + 1.8ft/s)

T = 40ft/(S - 1.8ft/s)

We can replace T in the second equation by the expression in the first one:

100ft/(S + 1.8ft/s) =  40ft/(S - 1.8ft/s)

now we can solve it for S.

100ft*(S - 1.8ft/s) = 40ft*(S + 1.8ft/s)

100ft*S - (100ft*1.8ft/s) = 40ft*S + (40ft*1.8ft/s)

100ft*S - 40ft*S = (100ft*1.8ft/s)+ (40ft*1.8ft/s)

S*(100ft - 40ft) = S*60ft = (100ft*1.8ft/s)+ (40ft*1.8ft/s)

S = ( (100ft*1.8ft/s)+ (40ft*1.8ft/s) )/60ft = (252ft^2/s)/60ft = 4.2 ft/s

The walking speed is 4.2 feet per second.

6 0
3 years ago
How many gallons of pure water should be added to 10 gallons of a solution containing 15% juice so that the remaining solution c
jok3333 [9.3K]

Answer:

20 gallons

Step-by-step explanation:

10 gallons of solution w/ 15% juice means 1.5 gal of juice

to make it into 5%, multiply 1.5 by 20

1.5 x 20 = 30

5% of 30 gallons is 1.5 since 10% of 30 is 3.

Since there was already 10 gallons, the # of gallons of pure water added should be 20 gal.

I hope this helps thanks

6 0
3 years ago
1/2 divided by N equals 1/3<br> what is N?
Veronika [31]

You said that                          (1/2)  /  N  =  1/3

Multiply each side by 'N' :      (1/2)          =  1/3 N

Multiply each side by  3 :        3/2           =        N

                                   or        1-1/2         =       N .


8 0
3 years ago
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What is the answer to this question<br> -5x-6=??
bekas [8.4K]

-5x-6=?

Is 5x-6

So, it is:

-1(x)

7 0
3 years ago
What is the length of segment AB
Lady bird [3.3K]

Answer: \large \boldsymbol {C) \ AB=\sqrt{41} }

Step-by-step explanation:

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8 0
3 years ago
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