- advertisement -

# Algebra help needed...again..

Discussion in 'Parents Off Topic' started by KeltonsMom, Jan 20, 2009.

1. ### KeltonsMomApproved members

Joined:
Sep 12, 2007
Messages:
3,605
I can't seem to wrap my brain around this, can any of you help?

2. ### MamaCApproved members

Joined:
Dec 9, 2006
Messages:
5,292
Tom and I both think it's 8. (25 X .32)...in other words she gets 32 hits for every 100 times at bat, so it's 8 for every 32 times up.

(But it took me till the end og my junior year to understand Algebra II. He's taking it now.)

3. ### KeltonsMomApproved members

Joined:
Sep 12, 2007
Messages:
3,605
I have two more...We both are stumped beyond belief  4. ### KeltonsMomApproved members

Joined:
Sep 12, 2007
Messages:
3,605
Okay, but the question asks how many hits she gets for every 25 at bat

5. ### mathcatApproved members

Joined:
Nov 17, 2006
Messages:
419
I agree with the answer of 8, but its 8 for every 25 times at bat.

To set it up as a proportion, use hits/times at bat = hits/times at bat

So, make sure that both ratios are set up with a numerator of hits and a denominator of times at bat. Consistensy is the ket to setting up proportions!

32/100 = x/25

32(25) = 100x

800 = 100x

8 = x

Anne could expect 8 hits if she had 25 times at bat with a batting average of 0.320.

6. ### MamaCApproved members

Joined:
Dec 9, 2006
Messages:
5,292

Yeah, that was my typo...sry.

7. ### MamaCApproved members

Joined:
Dec 9, 2006
Messages:
5,292
Sorry, I don't do graphing or slope. I'm gonna have nightmares now.

8. ### KeltonsMomApproved members

Joined:
Sep 12, 2007
Messages:
3,605
I am living in the nightmare right now, I have this sheet of paper in front of me with a graph and a slope I am very scared 9. ### mathcatApproved members

Joined:
Nov 17, 2006
Messages:
419
x + 3y ≤ 6
-x -x (subtract x from both sides)
3y ≤ -x + 6 (divide both sides by three)
3 3 (the dividing line on both sides did not show)
y ≤ -x/3 + 6/3
y ≤ (-1/3)x + 2

slope = m = Δy/Δx = rise/run = -1/3 (write a negative in front of the 1 and a positive in front of the three) (you can equivalently write a positive in front of the 1 and a negative in front of the 3 – either way the overall fraction is negative)
y intercept = 2

So, plot the point (0, 2) (this is on the y-axis, the up and down axis)
From that go down in the negative y direction 1 and over in the positive x direction to the right 3. You will land at (3, 1). Do this again to get to (6, 0).

Notice that the inequality was less than or equal to. Because of this draw a solid line through the points. If it were only less than or only greater than you would have drawn a dashed line.

For shading:
Find a point not on the line. Luckily (0, 0) is available. Substitute the x and y values from that ordered pair into the original inequality:
x + 3y ≤ 6
0 + 3(0) ≤ 6
0 + 0 ≤ 6
0 ≤ 6
This is a true statement so shade from your line in the direction that included (0, 0). If it were false you would shade the opposite side.

10. ### mathcatApproved members

Joined:
Nov 17, 2006
Messages:
419
Formatting can be frustrating sometimes on this board.

Where you see -x -x
One -x should be under the left hand side
The other -x should be on the right hand side

Where you see 3 3
One 3 should be under the left hand side
The other 3 should be on the right hand side

11. ### mathcatApproved members

Joined:
Nov 17, 2006
Messages:
419
Alternatively, the graph can also be determined by intercepts:

x + 3y ≤ 6

For x-intercept, let y = 0
x + 3(0) = 6
x = 6
So plot (6, 0)

For y-intercept, let x = 0
x + 3y =6
0 + 3y = 6
3y = 6
show that you divide both sides by 3
y = 6/3
y = 2
So plot (0, 2)

Draw a solid line as explained before and shade as explained before

12. ### moco89Approved members

Joined:
Mar 1, 2008
Messages:
2,430

Last edited: Jan 20, 2009
13. ### mathcatApproved members

Joined:
Nov 17, 2006
Messages:
419
Monica, make sure to correct

"The line would be y=-1X/2+2"

To

"The line would be y=-1X/3+2"

Which is equivalent to the (-1/3)x + 2 in my post (we were helping at the same time)

14. ### mathcatApproved members

Joined:
Nov 17, 2006
Messages:
419
For 4x - 8y = 8

First solve for y

4x-8y=8
subtract both sides by 4x
-8y = -4x + 8
divide both sides by -8
y = (1/2)x - 1 (notice that -4 over -8 gives the fraction 1/2)(notice that 8 over -8 gives -1)

so:
Slope = 1/2
y intercept = -1

Will post more in a moment

15. ### KeltonsMomApproved members

Joined:
Sep 12, 2007
Messages:
3,605
Thank you so much for your help..This is all Greek to me but Kelton just said "oh yeah, that is how it is done" I am sure glad he knows what you all posted..I am in the dark and still very scared  16. ### suzyq63Approved members

Joined:
Jan 9, 2008
Messages:
467
For the 2nd problem:

Change 4X-8Y=8 into the form of Y=mX+b
This would be:
-8Y = -4X + 8
Divide everything by -8, which gives you:
Y - 1/2X - 1

The perpendicular line's slope is the negative reciprocal of the original line's slope. Original line's slope is 1/2. Perpendicular line's slope would be -2.

Use the ordered pair given (1,2) to fill in for X and Y in the equation:

2 = -2(1) + b

Now solve for b:
2= -2 + b; b = 4

Perpendicular line equation is Y = -2X + 4

Hope this makes sense.

Last edited: Jan 20, 2009
17. ### mathcatApproved members

Joined:
Nov 17, 2006
Messages:
419
Okay, in the last post I showed that the slope of the original line is 1/2.

You need the slope of the new line which is perpendicular to the original line.

To do this, you need the negative reciprocal of the original slope

Original slope: 1/2
Slope of perpendicular: -(2/1) = -2

Now, you are given a point of (1, 2)

Use the formula y – y1 = m(x – x1)

We know that m = -2
We know that (x1, y1) = (1, 2)

Substitute:
y - 2 = -2(x - 1)
Distribute
y - 2 = -2x + 2
Add 2 to both sides (to isolate the y)
y = -2x + 4

18. ### mathcatApproved members

Joined:
Nov 17, 2006
Messages:
419
By the way, both Paula's method and mine are correct. Just go with whatever has been discussed in class.

19. ### BozziesMomApproved members

Joined:
Jul 16, 2008
Messages:
3,863
I don't do graphs or slopes either. I don't think I ever got one right.

20. ### moco89Approved members

Joined:
Mar 1, 2008
Messages:
2,430
Thanks, it is way easier for me to make errors while typing out math!

### Share This Page

 - advertisement -