math question

[teefRcool]

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Could someone please teach me how to do this

1) 20 is to 4y as 25x is to which of the following?
a) 5x/y
b) 5x
c) 5y/x
d) 5xy
e) x/5y

I keep missing these equation (perpendicular parralel problems) types of questions is there a trick to these or a basic review someone can help to teach me. Like the one below.

Which of the following is the equation of hte line that contains point (3,-1) and is perpendicular to the line y=3x + 3?
a) y=(-1/3)x
b) y=3x-10
c) y= 3-8
d) y= (-1/3)x + 2
e) y= (-1/3)x -2

Which line is parallel to the y-axis?
a) x=4y
b) x=(2/y)b
c) x=y+6
d) xy=2
e) xy=2 +4y-1

 

[mhl397]

1) 20 is to 4y as 25x is to which of the following?
a) 5x/y
b) 5x
c) 5y/x
d) 5xy
e) x/5y


This is how I would do it...

20/25x = 4y/?

100xy=20?
? = 5xy


When you're given a question like the other two...you have a couple options:
remember that y=mx + b, where b is your y-intercept and m is your slope (rise over run).
If you're trying to find perpendicular lines...just find the negative reciprocal of the slope given, ex. y = 2x + 7. the slope is 2 so the negative reciprocal would be -1/2 and the equation for the line perpendicular to y=2x + 7 would be y=-1/2x + 7

parallel lines have the same slope. ex) y = 2x + 5 and y = 2x + 7

your other option is to plug in numbers to the answer choices and draw the lines our yourself. if u had y=2x+5 and you dont know how to draw it out....plug in any number for x and solve for y. you know that this point is in the line, so choose another number for x and solve for y again. you'll get the line you're looking for.

by using 0 for x you can find out a Y intercept
by using 0 for y you can find out the X intercept.

thats the basics right there.
if i got any of that wrong please let me know.

 

[seoul]

Could someone please teach me how to do this

....

Which line is parallel to the y-axis?
a) x=4y
b) x=(2/y)b
c) x=y+6
d) xy=2
e) xy=2 +4y-1

There's no correct answer to this question. Where do you get this from?

There's actually no trick to solving these maths Q's except through lots of practices. Get any pre-college algebra book and work 40-50 questions alone on a single section. Remember you need speed and accuracy for QR on the DAT and not just understanding alone.

 

[Gasedo]

1) 20 is to 4y as 25x is to which of the following?
a) 5x/y
b) 5x
c) 5y/x
d) 5xy
e) x/5y


This is how I would do it...

20/25x = 4y/?

100xy=20?
? = 5xy


When you're given a question like the other two...you have a couple options:
remember that y=mx + b, where b is your y-intercept and m is your slope (rise over run).
If you're trying to find perpendicular lines...just find the negative reciprocal of the slope given, ex. y = 2x + 7. the slope is 2 so the negative reciprocal would be -1/2 and the equation for the line perpendicular to y=2x + 7 would be y=-1/2x + 7

parallel lines have the same slope. ex) y = 2x + 5 and y = 2x + 7

your other option is to plug in numbers to the answer choices and draw the lines our yourself. if u had y=2x+5 and you dont know how to draw it out....plug in any number for x and solve for y. you know that this point is in the line, so choose another number for x and solve for y again. you'll get the line you're looking for.

by using 0 for x you can find out a Y intercept
by using 0 for y you can find out the X intercept.

thats the basics right there.
if i got any of that wrong please let me know.

So the answer for problem 2 is y= -1/3x+2 right ?

 

[Baylor83]

So the answer for problem 2 is y= -1/3x+2 right ?

Answer is a not d

 

[howui3]

So the answer for problem 2 is y= -1/3x+2 right ?

in oder for the line to be parallel to the y-axis the equation must be:

x=any number (ex. x=5)

for a line to be parallel to the x-axis the equation must be:

y=any number (ex. y=5)

 

[teefRcool]

There's no correct answer to this question. Where do you get this from?

There's actually no trick to solving these maths Q's except through lots of practices. Get any pre-college algebra book and work 40-50 questions alone on a single section. Remember you need speed and accuracy for QR on the DAT and not just understanding alone.

Barrons

 

[teefRcool]

if u plug in those numbers for question two won't both A and B work?

 

[Gasedo]

in oder for the line to be parallel to the y-axis the equation must be:

x=any number (ex. x=5)

for a line to be parallel to the x-axis the equation must be:

y=any number (ex. y=5)

I know that, but I was talking about probl. 2, with the perpendiculat line

 

[seoul]

if u plug in those numbers for question two won't both A and B work?

Not sure which question you're referring to but I was saying that none of the answers in problem 3 is correct. And I think howui3 has provided great explanations on that.

I know that, but I was talking about probl. 2, with the perpendiculat line

Here's the solution just in case you would still need it:

Which of the following is the equation of the line that contains point (3,-1) and is perpendicular to the line y=3x + 3?

Comparing y = mx + b to the equation of line given,

m1 = 3

m1m2 = -1
m2 = -1/3

Using slope formula on the point (3,-1) given,

[y - (-1)] /[x - 3] = -1/3
y + 1 = (-1/3)x + 1
y = (-1/3)x

Correct Answer is therefore A.