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uria: Newbie | Next Rank: 10 Posts; Posts: 6; Joined: Tue Jan 22, 2008 10:11 am

please help

by uria » Sun Mar 30, 2008 5:40 pm

DS Question:
On the number line, the distance between point A and point C is 5 and the distance between point B and C is 20. Does point C lie between point A and point B?
1. The distance between point A and point B is 25.
2. Point A lies to the left of B.

Quote

Source: Beat The GMAT — Data Sufficiency | Sun Mar 30, 2008 5:40 pm

codesnooker: Legendary Member; Posts: 543; Joined: Fri Jan 18, 2008 1:01 am; Thanked: 43 times; GMAT Score:580

by codesnooker » Sun Mar 30, 2008 11:03 pm

Answer: (D). Both the statements are alone sufficient.

Solution:

Check the attached image.

On the number line there are only two conditions where B can lie, marked as B and B'.

As first statement state: distance between A and B is 25 => B' not possible as distance between A and B' is only 15 which contradicts 1st statement. => C lies between A and B.

Statement 2 state, Point A lies left to B => C lies between A and B.

Image is self explanatory, as B' is not possible at all with any one of the mentioned statement

Attachments

: numberline

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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

by Stuart@KaplanGMAT » Mon Mar 31, 2008 8:40 am

codesnooker wrote:Answer: (D). Both the statements are alone sufficient.

Solution:

Check the attached image.

On the number line there are only two conditions where B can lie, marked as B and B'.

As first statement state: distance between A and B is 25 => B' not possible as distance between A and B' is only 15 which contradicts 1st statement. => C lies between A and B.

Statement 2 state, Point A lies left to B => C lies between A and B.

Image is self explanatory, as B' is not possible at all with any one of the mentioned statement

I agree that statement (1) is sufficient.

However, for statement (2), why couldn't it go:

C----5------A-------------15--------------B

to get a "no" answer?

In fact, since we don't have any directional info other than statement (2), how can it possibly matter if A is to the left of or to the right of B? Even in your sketch for statement (1) it could have gone:

B----------20------------C----5----A

or

A-----5----C------------20---------B

(1) is sufficient, but (2) isn't: choose (b).