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Jeffrey Spoon
science forum beginner

Joined: 12 Jul 2006
Posts: 2

Posted: Wed Jul 12, 2006 3:04 pm    Post subject: Simplifying Algebraic expression

Don't laugh, I have a simpleton question. I have an expression:
(3+5) / (15-3) / (4/3) + (9/4) - (11/ x X = 0

The answer given to simplifying this is:

22 - 11 X = 0

Though I'm not sure how to get this. The furthest I got was:

8 / 12 / 86/24 - 33/24

How that becomes 22 - 11 is a mystery to me.

Thanks,

--
Jeffrey Spoon
Dave L. Renfro
science forum Guru

Joined: 29 Apr 2005
Posts: 570

Posted: Wed Jul 12, 2006 3:07 pm    Post subject: Re: Simplifying Algebraic expression

Jeffrey Spoon wrote:

 Quote: Don't laugh, I have a simpleton question. I have an expression: (3+5) / (15-3) / (4/3) + (9/4) - (11/ x X = 0

[snip rest]

Since division is not an associative operation, you need
to insert parentheses to avoid ambiguity.

Dave L. Renfro
amzoti
science forum beginner

Joined: 18 Apr 2006
Posts: 33

Posted: Wed Jul 12, 2006 3:28 pm    Post subject: Re: Simplifying Algebraic expression

Jeffrey Spoon wrote:
 Quote: Don't laugh, I have a simpleton question. I have an expression: (3+5) / (15-3) / (4/3) + (9/4) - (11/ x X = 0 The answer given to simplifying this is: 22 - 11 X = 0 Though I'm not sure how to get this. The furthest I got was: 8 / 12 / 86/24 - 33/24 How that becomes 22 - 11 is a mystery to me. Thanks, -- Jeffrey Spoon

Hello,

division is not an associative operation and your parentheses are
lacking and ambiguous.

Here is what you probably meant:

((3+5) / (15-3) / (4/3)) + (9/4) - (11/ x X = 0

Simplify the first set of parentheses:

((3+5) / (15-3) / (4/3)) = (8/12) / (4/3) = (8/12) * (3/4) = 2/4 = 1/2

Now we have:

(1/2) + (9/4) - (11/ X = 0

(1/2) + (9/4) = (11/4), so

(11/4) - (11/ X = 0

Multiply 8:

8 ( (11/4) - (11/ X = 0), yielding

22 - 11 X = 0

11X = 22

X = 2

I am not sure this really helps you, but hope you learn something from
it.
science forum beginner

Joined: 07 May 2006
Posts: 38

Posted: Wed Jul 12, 2006 3:59 pm    Post subject: Re: Simplifying Algebraic expression

On Wed, 12 Jul 2006 15:04:46 GMT, Jeffrey Spoon
<JeffreySpoon@hotmail.com> wrote:

 Quote: Don't laugh, I have a simpleton question. I have an expression: (3+5) / (15-3) / (4/3) + (9/4) - (11/ x X = 0 The answer given to simplifying this is: 22 - 11 X = 0 Though I'm not sure how to get this. The furthest I got was: 8 / 12 / 86/24 - 33/24 How that becomes 22 - 11 is a mystery to me. Thanks,

In case you're not familiar with 'order of operations' and 'operator
precedence', here's a link that provides an introduction:

<http://en.wikipedia.org/wiki/Order_of_operations>

Evaluating ...

(3+5) / (15-3) / (4/3) = 8 / 12 / (4/3) = 1/2

1/2 + 9/4 = 11/4

11/4 - 11 x / 8 = 0

22 - 11 x = 0

HTH
Jeffrey Spoon
science forum beginner

Joined: 12 Jul 2006
Posts: 2

Posted: Sat Jul 15, 2006 4:12 pm    Post subject: Re: Simplifying Algebraic expression

amzoti <amzoti@yahoo.com> writes
 Quote: Hello, division is not an associative operation and your parentheses are lacking and ambiguous. I am not sure this really helps you, but hope you learn something from it.

That helped a lot, once I dusted off an old maths book and realised the
inversion and multiplication you do for fraction division. I should say,
about the brackets, they were not in the original book which I had just
copied. Thanks (and to Badger as well).

--
Jeffrey Spoon

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