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jamesk486: Master | Next Rank: 500 Posts; Posts: 141; Joined: Wed Mar 28, 2007 9:24 pm; Thanked: 2 times; Followed by:1 members

gmat prep question

by jamesk486 » Wed May 09, 2007 7:01 pm

If x is a positive integer, what is the least common multiple of x, 6 and 9?(1) LCM of x and 6 is 30
(2) LCM of x and 9 is 45

In the xy plane, at what two points does the graph of y= (x+a)+(x+b)
(1) a+b=-1
(2) the graph intersects the x=axis at at (0,6)

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Source: Beat The GMAT — Data Sufficiency | Wed May 09, 2007 7:01 pm

jayhawk2001: Community Manager; Posts: 789; Joined: Sun Jan 28, 2007 3:51 pm; Location: Silicon valley, California; Thanked: 30 times; Followed by:1 members

Re: gmat prep question

by jayhawk2001 » Wed May 09, 2007 9:46 pm

jamesk486 wrote:If x is a positive integer, what is the least common multiple of x, 6 and 9?(1) LCM of x and 6 is 30
(2) LCM of x and 9 is 45

Is it D?

1 - sufficient. LCM of x and 6 is 30. So, x has to be 5, 10, 15 or 30.
In each of the cases, LCM of x,6,9 is 90

2 - sufficient. LCM of x and 9 is 45. So, x can be 5, 15 or 45.
Again, in each case, LCM of x,6,9 is 90.

jamesk486 wrote: In the xy plane, at what two points does the graph of y= (x+a)+(x+b)
(1) a+b=-1
(2) the graph intersects the x=axis at at (0,6)

I'm guessing the equation is y = (x+a)(x+b) since it is asking for
2 points (meaning there should be 2 values and hence a quadratic
equation)

Also, item 2 should be "intersects the y axis" since the x value is 0.
You can't have the graph intersect the x-axis at a non-zero y value
:roll:

Can you please check the question