Question

4.

(1 pt)
The distance traveled by a sound wave through a substance is proportional to time. The graph shows this relationship for several substances.

Which substances have a unit rate greater than 2 km/s?

Choose all answers that are correct.



A.
cork

B.
glass

C.
lead

D.
titanium

Answer 1

2 km/s means\[\frac{2km}{1second}\]So it's a slope... you just need to calculate the slope for the other lines and see which ones match :-)

Answer 2

i just want to understand the question plz help

Answer 3

I already helped you... I can't tell you step-by-step, you won't learn. :-\
Where are you confuse?

Answer 4

*confused

Answer 5

what do you mean bye i just need to calculate the slope for the other lines and see which ones match

Answer 6

2 km/s is a slope, 2 km/ 1 s or 2/1
you know how to calculate slope yes?

Answer 7

no im trying to learn

Answer 8

Okay. Well, this is the formula they usually start out with:\[\frac{y_{2}-y_{1}}{x_{2}-x_{1}}\text{with two given points}(x_{1},y_{1}),(x_{2},y_{2})\]

Answer 9

Are you following? :-)

Answer 10

yes

Answer 11

Okay. So they're asking for any lines that have a slope ABOVE that of 2, or 2/1... this will be a hassle but I think you have to solve for the slopes of ALL the lines. ^-^;

Answer 12

ok

Answer 13

thank you

Answer 14

... oh shoot
You don't have enough points to get slope by that formula...

Answer 15

Well in that case we just do the point-slope formula:\[y-y_{1}=m(x-x_{1})\]
Same variables apply! The x and y without a little number are left the same; don't change those :-)

Answer 16

so is it a b d

Answer 17

o_o
Have you applied the point slope formula I gave you?

Answer 18

yes is a b d correct

Answer 19

Ignoring the previous since we only have one point per line to work off of...let's try the top line with point (10,60). Here's how it looks in the equation -\[y-60=m(x-10)\]We need to isolate the y...
Oh, you did this already? o_e

Answer 20

where did i get the medal from did you give me one

Answer 21

The first formula I gave you doesn't work, there's not enough information to put into the equation :-P

Yep! For being involved in learning and trying to understand concepts. You earned it :-

Answer 22

:-D* (wow that was a terrible typo lol)

So do you know how to apply the point slope formula to the respective lines? :-)

Answer 23

ok thank you

Answer 24

Okay... are you good with the point-slope formula or should I keep going

Answer 25

can you ckeep going so i fully understad the problem

Answer 26

keep

Answer 27

Okay... continuing where we left off, the point-slope formula for the topmost line with point (10,60):\[y-60=m(x-10)\]We need to isolate the y and put the equation into this format:\[y=mx+b\]Can you do that or should I keep going :-P

Answer 28

i dont understand that part im not good at that part

Answer 29

wait its not a so does that make it b ,c,d

Answer 30

Okay, so we have too much on the left side, we want only y, yes?\[y-60=m(x-10)\]Let's first simplify the right side by using the Distributive Property:\[y-60=mx-m(10)\]which leads to\[y-60=mx-10m\]Now, this might be confusing, but we have to reverse the Distributive Property now... also known as "factoring out". We'll be removing x from the right side -\[y-60=m(x-10)\]Are you following so far?

Answer 31

ok

Answer 32

Okay, so now we need to have ONLY y on the left side, so we'll move the 60 over by subtracting it from both sides. -(-60) becomes +60...\[y=m(x-10)\]
...wait I think I messed up somewhere

Answer 33

Let me check and then get back to you on this... @ _ @;

Answer 34

hold on i fell bad how do i give you a medal

Answer 35

you are so helpful

Answer 36

LOL
Aww no honey, it's okay ; - ;
Though you just hit the blue button by the little medal icon, it says "Best Response" :-D

Answer 37

ok

Answer 38

im new here

Answer 39

so back to the qustion is it b c d

Answer 40

I need to look at my own work before I get back to you on that... I'm sorry ; -;

Answer 41

its ok

Answer 42

> <;;

Answer 43

Ugghhh.... okay I'm gonna be a lazy butt and Google this lol

Answer 44

ok

Answer 45

Uh... I guess you could just use the one point and the origin as the second point, on each line... since all lines start from the origin :-P

Answer 46

ok

Answer 47

So it would be (0,0) and (10,60) for the top line. The equation I gave you first should work...\[\frac{y_{2}-y_{1}}{x_{2}-x_{1}}\]

Answer 48

ok thank you i got the awnser

Answer 49

Here is a link to the same problem... http://brainly.com/question/891426
Oh? Was the answer right? :-D

Answer 50

yes thank you

Answer 51

I believe the answer is Glass and Titanium, so B and D...?

Answer 52

a b d

Answer 53

EH?? D:

Answer 54

That's weird D: because the slope for A) cork is 10/5 = 2 o_e

Answer 55

it is ok

Answer 56

I-I mean 5/10 for the cork...

Actually, since everything is 10, we just move one decimal space forward...
titanium: 60/10 = 6
glass: 40/10 = 4
lead: 12/10 = 1.2
cork: 5/10=0.5 (or 1/2) ???

Yeah... that's just two answers. A doesn't work...

Answer 57

I don't want you to get the wrong answer ; ~;

Answer 58

i sumited got80% it was b d

Answer 59

Yeah... it was only two answers
D': I'm sorry

Answer 60

Oh! Does it let you try again ?? :-D

Answer 61

its ok

Answer 62

:-(

Answer 63

i got 80 % thats good

Answer 64

Weeeell... I guess :-\
Lol. I grew up being told that anything under 98% sucks. 90% is the lowest I can go without being "bad" x'D

But yeah, you're good I guess :-P

Answer 65

80% and higher is good for 7 th grade i guess

Answer 66

Alright ^-^

Answer 67

ok bye

Answer 68

• D •)/

Answer 69

what does that mean

Answer 70

ok bye i have to close it

Answer 71

it means bye with a cute face lol