View Full Version : What is the average of the expressions

redranger7018

07-15-2006, 12:11 PM

What is the average of the expressions;

4x, 2x+1, x-4, and -3x-1

A) x+1

B) 4x-1

C) x-1

D) 4x-4

E) -24x+4

Been having the most trouble figuring out how to do this types of equasions. The study guide say's to add up the like terms and then divide, but my answers don't match up with the questions list answers.

jonboy

07-15-2006, 12:17 PM

Show us what you have done so far.

redranger7018

07-15-2006, 12:42 PM

What is the average of the expressions 5x + 3, 8x - 2 and 5x + 5?

A ) 18x + 10

B ) 18x + 6

C ) 5x - 3

*D ) 6x + 2

The correct answer was D

To solve the problem:

What is the average of the expressions

5x + 3, 8x - 2, 5x +5?

Answer: 6x + 2

Explanation:

Add up the x-terms and you should get 18x.

Then add up the constants and you should get 6.

Now divide these two terms by 3: 6x +2.

==

This is what I got when I tried this one.

5x + 3

8x - 2

5x + 5

Add like terms:

5x + 8x + 5x = 18x

Add other like terms:

3 + 2 + 5 = 10

Divide terms:

18x divided by 3 = 6x

10 divided by 3 = 3

Combined terms:

6x + 3

==

The above guide says that the answer should be 6x + 2. What is my mistake?

jonboy

07-15-2006, 12:48 PM

First of all I would like to thank you for replying and not just giving up. :D

Add other like terms:

3 + 2 + 5 = 10

That should be a -2. Just a simple mistake no biggie but make sure you learn from it.

So: (3)+(-2)+5=6

Hence: \frac{18x+6}{3}

So solve that.

I divided by three since we have three terms.

redranger7018

07-15-2006, 01:06 PM

Thanks jonboy, for the help. the -2 makes it work out better. Still having trouble with this one as well.

What is the average of the expressions;

4x, 2x+1, x-4, and -3x-1

A) x+1

B) 4x-1

C) x-1

D) 4x-4

E) -24x+4

==

4x + 2x + x + -3x = 4x

1 + 4 + 1 = 6

4x divided by 4 = 1x

6 divided by 4 = 2

I get: 1x + 2, but it does not match the list of possible answer, what am I doing wrong?

jonboy

07-15-2006, 01:15 PM

Our original Problem:

4x, 2x+1, x-4, -3x-1

You added the x's stupendously. :D

But you must recognize that not all the number you add are gonna be positive.

The 4 has a negative in front of it so it is -4.

The 1 has a negative in front of it so it is -1.

So add (-4)+(-1)+(1)

The -1 and +1 cancle each other out so our intergers equal -4.

So: \L \frac{4x-4}{4}

Can you solve that?

redranger7018

07-15-2006, 02:04 PM

Hi to all, and thanks for all your help. Ok I tried this again with the negatives in place, but I'm not sure if I getting it right.

4x + 2x + x + -3x = 4x

1 + -4 + -1 = -4

D). 4x -4, is this the correct answer?

This matches the answer list for answer D), but that's before I didvided. This is what, I get when, I divide by 4. The question is should, I be dividing or not?

4 / 4 = 1

-4 / 4 = -1

1x -1, no match to answer list.

redranger7018

jonboy

07-15-2006, 02:08 PM

NO 4x-4 is not the answer.

Since you are finding the AVERAGE you must divide 4x-4 by 4 since you have 4 terms.

Just like if you had 1,2,3,4 and you wanted to find the mean (or average).

1+2+3+4=10

(10/4)=5/2

1x-1=x-1 The 1 is understood in front of the x. Ok?

Just like x+2x+3x=6x

The one is understood in front of the x.

So our answer would be c. x-1

redranger7018

07-15-2006, 02:19 PM

Ok then, 4x -1 is the only other answer if I'm geting this write.

jonboy

07-15-2006, 02:22 PM

Ok then, 4x -1 is the only other answer if I'm geting this write.

No cuz x-1 is 1x-1 which is what you got.

4 / 4 = 1

-4 / 4 = -1

1x -1, no match to answer list.

The one is understood just like here:

4x + 2x + x + -3x = 4x

4x+2x+1x-3x=4x

The both get the same answer cuz the 1 is understood in front of the x. Just like there is a one exponent for the x but you do not write it.

redranger7018

07-15-2006, 02:32 PM

Ok need to think in negative terms all the way throw the equation.

x - 1

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