# algebra

Hi I'm having trouble with this question I don't understand it at all. This is the question:
Suppose y varies directly with x, and y = 15 and x = 5. Write a direct variation equation that relates x and y. What is the value of y when x = 9?

If somebody could help me & let me know what a direct variation equation is I'll be very grateful to you! I don't know what this is, I missed the last 2 days of school & that must have been when the teacher went over this. My friend tried to help me but he doesn't know what direct variation means either. Thank you if you know anything about this :)))

1. 0
1. It's homework due tomorrow & I have practice in an hour so if you can help me before then I'll be so grateful!

posted by Abi Cartright
2. Okay I found something on this, so you do 15=5k then divide both sides by 5 to solve for k so you get k=3 then do y=3x but put what they gave, so x=9 so then y=3(9) so is the answer y=27??

posted by Abi Cartright
3. x = yk

5 = 15 * 1/3

9 = y * 1/3

Although I use a slightly different process, our answers are the same.

posted by PsyDAG
4. Whenever you have a direct variation of something like
(.....y....) varies directly with (.....x.....) we can say
y = kx

Usually you will be given one case where that is true, in your case x = 5 and y = 15.
So sub that in ...
15 = 5k
k = 3

so now we know the variation equation is y = 3x
The question was : What is the value of y when x = 9?
so let's put in x = 9
y = 3(9) = 27

If the variation is inversely proportional,
we say y = k(1/x) and proceed as before.

posted by Reiny
5. Yay, so I was right? Thank you so much

posted by Abi Cartright

## Similar Questions

1. ### Math- Need Help..

I'm having trouble with a question from one of my math assignments and it's driving me crazy. Its: -2/5x - 9 < 9/10 (two-fifths and nine-tenths) I tried doing it a few times, it might be easier than it looks and I just don't
2. ### Algebra

this isn't the same question as my last post!! it's the second out of three. Hello! I'm looking over one of my tests and trying to see how to do things I got wrong, but I'm having trouble with three of the questions. Here's one of
3. ### Math

I'm using the quadratic equation and I understand how to use it, but the format my text book gives the answers in is what I don't understand. If I have (2+/-Sqrt(8))/2 I know that x can either equal 2.41 or -0.14 However, my
4. ### re -same question again

sorry to post this question again but i am having trouble finding evidence of what jesus did not do . i don`t really understand the question like i mentioned in my last post does it mean that he did not get married or have
5. ### Science

Is there an easier way to understand how to convert gallons to liters I am having problems understanding the whole metric conversion process. I don't know what method you are using so I don't know if I know an easier one or not. I
6. ### Biology

I had a Bio lab about gel electrophoresis and PCR. for each lab, we have to make up thoughtful, detailed questions. You don't have to answer the questions so please don't go through the trouble by answering them. The first
7. ### CHEM- KINETICS

The rate constant for a reaction is 4.65 L mol-1s-1. The overall order of the reaction is: zero first second third I am having trouble with the order of reactions. I don't understand this question. this is an assignment question
8. ### AP Calculus AB

Set up, but do not evaluate, the integral which gives the volume when the region bounded by the curves y = Ln(x), y = 1, and x = 1 is revolved around the line y = -1. I don't understand the washer thickness topic which is why im
9. ### To gina

I have deleted your post. PLEASE do not put personal information (names, phone numbers, and that kind of thing) on this site. The Internet is not a safe place for that information. I am sorry you arre having trouble with
10. ### english

I'm having trouble understanding how to answer this question about a reading I did, the question is "could Joe have anticipated John's approach?" could anyone possibly help me understand what this question means better.....thanks

More Similar Questions
{"found_math": false, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 0, "mathjax_display_tex": 0, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0}