GRE Math - Quantitative Comparison - QC Strategy - Matching Operations

[@aakashgill97]

Team Greenlight is so professional! Awesome.

[@GreenlightTestPrep]

Thanks Aakash!

[@saffanatranslation2153]

@1:43 when we try plugging in numbers method we get contradictory values which is supposed to be D

[@GreenlightTestPrep]

Are you sure you mean 1:43 in the video? I don't see what you're referring to

[@magikarpbeater]

at 3:44 dividing by 3, should be 5/3 rather than just 3. Doesnt matter, love your content either way :)

[@R_Ash131]

Not the original value. You should divide 6 to 3 to get 2 on the left hand side, and 9 to 3 to get 3 on the right hand side. Hope that help you.

[@GreenlightTestPrep]

​@@R_Ash131 beat me to it. As he pointed out, we're looking at successive changes. So, for Quantity B, we start with 5. Add 8 to 5 to get 13. Subtract 4 from 13 to get 9. Divide 9 by 3 to get 3. Multiply 3 by 6 to get 18.

[@micahgriggs1761]

When I performed this problem on my own, I got the variable w under B and -1 under A.

[@micahgriggs1761]

Am I supposed to keep the variable on the left side of the inequality as given?

[@GreenlightTestPrep]

Can you tell me the steps you took to get there?

[@micahgriggs1761]

@@GreenlightTestPrep Step 1: Subtract 7w from w to get -6w under B. Step 2: Add 2 to 4 to get 6 under A. Step 3: Divide -6w by -6 on both sides to get w under B and -1 under A. Thus, A: -1 and B: w. Hence, the answer I chose was B.

[@TheIgnoredGender]

I tell my students that they can also multiply or divide both columns by a negative but they must remember to flip their answer afterward.

[@GreenlightTestPrep]

Yeah, I've seen that strategy. I feel that it causes more problems than it solves.

[@alienangel777]

Could you just stop at the first step after subtracting w from both sides, since we know that w is greater than 0, we can tell that 6w + 4 is greater than -2?

[@GreenlightTestPrep]

Absolutely - we can stop as soon as it appears that we have sufficient information to compare the two quantities. I kept going in order to demonstrate the strategy that the video highlights. Cheers, Brent

[@blaice7365]

when doing the 2x and 3x question, you took too many additional steps. Simply multiplying each side by 1, and then -1 (since x is not given a distinct value, integer, positive, negative, or otherwise.) and you get A and then B, therefore, you know within seconds that the answer is D. There is no need to subtract any amount of x from either side.

[@GreenlightTestPrep]

I think you're missing the point of this video. It's meant to show a technique to consider when tackling GRE Quantitative Comparison questions. The technique, Matching Operations, is demonstrated throughout the video. So, while plugging in 1 and -1 for x is a valid approach, we are covering a different approach here. For more information about plugging in values, we have this video: kzbin.info/www/bejne/Y6G1foF7eb-DeNU

[@haroonahmed2156]

Can we perform operations only on one quantity to make it similar to second quantity? Like If we are given 2 fractions to compare then we typically make numerator or denominator of only one fraction similar to numerator or denominator of other by performing certain operations?

[@BossofBosses111]

It's like doing an equation, what you do to one side you need to do to the other

[@nirajkc224]

you earned my respect !☺

[@GreenlightTestPrep]

Excellent!

[@ngoanho4558]

Some segments in the video are stamped not adjacent to each other

[@srujenkrishna5738]

as u r telling everytime the positive is the answer but in some cases the negative is also the answer

[@GreenlightTestPrep]

Srujen Krishna I'm not sure what you mean. Can you please elaborate?