Concept not clear

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Which quadrants if any do not contain any points on the line represented by x=10y

[snigdha1605]

It helps to roughly plot this line on the graph by plugging values

For eg :

when x= 0 y = 0
when x= 10 y = 1
when x= -10 y = -1
and so on...

The line passes through quands 1 and 3

Quandrants 2 and 4 DO NOT contain any points on the line x=10y

[Jim@StratusPrep]

Key is that there is that the intercept is the origin and the slope is positive. Thus, the line goes through 1 and 3, but not 2 and 4.

[Brent@GMATPrepNow]

Which quadrants if any do not contain any points on the line represented by x = 10y

It might help to first rewrite the equation x = 10y in slope y-intercept form (y = mx + b), where m is the line's slope and b is the y-intercept.

Take x = 10y
Divide both sides by 10 to get: (1/10)x = y
In other words, y = (1/10)x + 0
So, the line's slope is 1/10 and its y-intercept is 0 (in other words, the line passes through the origin).
So, it looks like this.

As you can see, the line passes through quadrants I and III only

Cheers,
Brent

[mgm]

Jim is there a rule around Slope and Intercept that can help figure out the solution fairly quickly ?

[Jim@StratusPrep]

Y=mx +b

M is the slope, b is the y-intercept. You simply need to rearrange the equation to this format. You get y=1/10x. 1/10 is positive and there is no b value (in other words it is 0, which is the origin).

[[email protected]]

Hi mgm,

The "quick" way to answer these types of questions involves 2 pieces of information:

1) The Slope of the line
2) The Y-intercept of the line

With slope:
-A positive slope means the line hits I and III and will hit II OR IV, but not both
-A negative slope means the line hits II and IV and will hit I OR III, but not both
-A flat line (0 slope, left/right) hits I and II OR III and IV
-An infinite slope (up/down) hits I and IV OR II and III

**The exceptions are lines that ARE the x-axis or y-axis**

The Y intercept combines with the slope to narrow the options (and show you what quadrant DOESN'T get hit by the line).

GMAT assassins aren't born, they're made,
Rich