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Mjkourtis: Junior | Next Rank: 30 Posts; Posts: 20; Joined: Tue Feb 07, 2012 3:31 am

by Mjkourtis » Wed Jul 11, 2012 3:25 pm

Does y=3x+2 contain (r,s)?

(1) (3r+2-s)*(4r+9-s)=0
(2) (4r-6-s)*(3r+2-s)=0

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Source: Beat The GMAT — Problem Solving | Wed Jul 11, 2012 3:25 pm

Jim@StratusPrep: MBA Admissions Consultant; Posts: 2279; Joined: Fri Nov 11, 2011 7:51 amFollowed by: 266 members; Location: New York; Thanked: 660 times; GMAT Score:770

by Jim@StratusPrep » Wed Jul 11, 2012 3:44 pm

If you rearrange the equation you get 0 = 3x + 2 - y.

1) One of the two expressions must equal 0 for the product of the two expression to equal 0. However, we cannot be sure if it is the first one, which matches the equation above, or the second. INSUFFICIENT

2) One of the two expressions must equal 0 for the product of the two expression to equal 0. However, we cannot be sure if it is the second one, which matches the equation above, or the first. INSUFFICIENT

Putting them together we know that it must be the expression that matches the equation. There is no way for 4r - 6 - s and 4r + 9 - s to both equal zero. You will notice that 4r - s is in both expressions and one is increased by 9 and the other decreased by 6.

The answer is C.

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karthikpandian19: Legendary Member; Posts: 1665; Joined: Thu Nov 03, 2011 7:04 pmFollowed by: 70 members; Thanked: 165 times

by karthikpandian19 » Wed Jul 11, 2012 8:52 pm

I didnt understand the explanation that you had provided for the C (two statements combined)

Jim@StratusPrep wrote:If you rearrange the equation you get 0 = 3x + 2 - y.

1) One of the two expressions must equal 0 for the product of the two expression to equal 0. However, we cannot be sure if it is the first one, which matches the equation above, or the second. INSUFFICIENT

2) One of the two expressions must equal 0 for the product of the two expression to equal 0. However, we cannot be sure if it is the second one, which matches the equation above, or the first. INSUFFICIENT

Putting them together we know that it must be the expression that matches the equation. There is no way for 4r - 6 - s and 4r + 9 - s to both equal zero. You will notice that 4r - s is in both expressions and one is increased by 9 and the other decreased by 6.

The answer is C.

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shekhar.kataria: Master | Next Rank: 500 Posts; Posts: 268; Joined: Mon Mar 15, 2010 12:10 am; Thanked: 13 times

by shekhar.kataria » Thu Jul 12, 2012 10:53 am

Just about thinking logically, you can solve this question in 30 sec.

* you need 2 equations to find out valusef two variables, here r and s.

ST1. Can't be sufficeint because of the above reason.
ST2 Cant be sufficient because of the above reason.

Taken together :- now that u have two equations and two variables, it is for sure that you will get some value of r and s. ( Remember in DS u dont need to find out the value, just find out that the data is suficient of not ).

Now this point (r,s) will either lie on the line or not. In either case, it is a definite answer. and therefore C.

Mjkourtis wrote:Does y=3x+2 contain (r,s)?

(1) (3r+2-s)*(4r+9-s)=0
(2) (4r-6-s)*(3r+2-s)=0

Restlessness and discontent are the first necessities of progress.--Thomas A. Edison

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