indirect proportion

[Emilyneedshelp]

y is directly proportional to x
when y = 144, x=12
work out what y is when x=7
here's what I did,
y=kx
144=kx12
12=k
y=12x7
does
7y = 12
or does
y = 84
????

 

[Dr.Peterson]

First, please don't use "x" to mean both a variable and multiplication; that's very confusing! The standard symbol to use in typing is "*", or just omit the symbol entirely when you can.

So you are asking, if y = 12x, so that when x = 7, y = 12*7, what is y?

The answer is that you just carry out the indicated operation: multiply 12 times 7 and get 84.

7y = 12 is an entirely different statement. Is there some reason you thought it might be appropriate?

 

[Emilyneedshelp]

umm well according to the renowned CGP books, the answer was, in fact, 7y = 12. If you have an issue with this then take it up with the company. I am simply an innocent bystander to this insanity. I don't think it was at all necessary for you to take that tone with me, "Dr" Peterson. I don't know what your Ph.D. is in but its clearly not people skills. Appreciate your "help".

-Emily

 

[MarkFL]

umm well according to the renowned CGP books, the answer was, in fact, 7y = 12. If you have an issue with this then take it up with the company. I am simply an innocent bystander to this insanity. I don't think it was at all necessary for you to take that tone with me, "Dr" Peterson. I don't know what your Ph.D. is in but its clearly not people skills. Appreciate your "help".

-Emily

Hello Emily,

I honestly do not see where Dr. Peterson has taken any kind of ill tone in his post. He simply asked, even saying "please," that "x" not be used as a symbol for multiplication because it can easily be confused with a variable. Also, there was no indication in your original post where "7y = 12" came from, and so he simply asked about that.

We do expect our helpers to be civil when posting help, but I can assure you Dr. Peterson is, in my opinion, one of our best helpers. I've never looked at one of his posts and thought his tone was inappropriate. He knows his math, and he's always struck me as a very helpful and diplomatic individual.

 

[Dr.Peterson]

umm well according to the renowned CGP books, the answer was, in fact, 7y = 12. If you have an issue with this then take it up with the company. I am simply an innocent bystander to this insanity.

Please explain the context of your question. Are you saying that your book gave this problem, and said that 7y = 12 is the answer, while you believe it is 84? If so, then I agree with you; and you and I are perhaps both "innocent bystanders to this insanity".

I'd like to figure out what this is about. Errors in textbooks are more common than you might think; so are misunderstandings of what a book says. At this point I have no idea.

Perhaps you need to quote the problem using the exact words, in case you didn't already, and likewise quote what the book says in response.

 

[Steven G]

umm well according to the renowned CGP books, the answer was, in fact, 7y = 12. If you have an issue with this then take it up with the company. I am simply an innocent bystander to this insanity. I don't think it was at all necessary for you to take that tone with me, "Dr" Peterson. I don't know what your Ph.D. is in but its clearly not people skills. Appreciate your "help".

-Emily

Emily,
I have seen Dr Peterson go out of his way to be civil to students even after they unjustly attacked him. Dr Peterson attitude I am sure was to try his very best to see why the book had 7y=12 by simply asking you why you thought 7y=12 was appropriate. He could have just said that the book was wrong and be done. But instead he put you first and tried to see how that answer in the book could be correct.
Please understand that you misunderstood his comments