slope and intercepts

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salma: Junior | Next Rank: 30 Posts; Posts: 19; Joined: Sat Nov 03, 2007 5:54 pm

slope and intercepts

by salma » Sun Jan 27, 2008 8:05 am

Hi,
Can please tell how to deal with this question:
In the xy-plane, line k has positive slope and x-intercept 4. If the area of the triangle formed by line k and the 2 axes is 12, what is the y-intercept of line k?
-6/-4/-3/3/6
I answered 6 but the correct answer is -6.
I also have difficulties with the following question:
Is the hundredths digit of the decimal d greater than 5?
1) The tenths digit of 10 is 7
2) The thousandths digit of d/10 is 7

Thank you so much for your help.

Quote

Source: Beat The GMAT — Data Sufficiency | Sun Jan 27, 2008 8:05 am

Stuart@KaplanGMAT: GMAT Instructor; Posts: 3225; Joined: Tue Jan 08, 2008 2:40 pm; Location: Toronto; Thanked: 1710 times; Followed by:614 members; GMAT Score:800

Re: slope and intercepts

by Stuart@KaplanGMAT » Sun Jan 27, 2008 10:39 am

salma wrote:Hi,
Can please tell how to deal with this question:
In the xy-plane, line k has positive slope and x-intercept 4. If the area of the triangle formed by line k and the 2 axes is 12, what is the y-intercept of line k?
-6/-4/-3/3/6
I answered 6 but the correct answer is -6.

Positive slope means that the line goes from bottom left to top right.

Since the line crosses the x-axis at a positive coordinate (+4), we know that it must cross the y-axis at a negative coordinate.

I line that passed through (0,6) and (4,0) would have a negative slope, so the y-int can't be +6.

* * *

For your second question, I think that there's a "D" missing in one of the statements.