#8 From great (Q47?) to incredible (Q51?!) on GMAT DS: GMAT Ninja Series 2, Video 8

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#8 From great (Q47?) to incredible (Q51?!) on GMAT DS: GMAT Ninja Series 2, Video 8

Рет қаралды 39,164

GMAT Club

Күн бұрын

Пікірлер: 62

@ramgupta6709 2 жыл бұрын

Great job, GMAT Ninja. 1 Week to go for my gmat and still this guy's free videos help me more than my coaching people! :)

@jded1346 5 жыл бұрын

is Q1 a valid gmat Q? statement 1 says d=7; this implies c = sqrt(29-49) which is imaginary....so statement 2 would be inconsistent since statements cannot contradict on the GMAT

@LordLevan 5 жыл бұрын

Was thinking about it too

@LamboWalker23 3 жыл бұрын

2 years late but see, even if its square root of negative we will still get 2 possible values of the square root with 1 positive and the other negative. So statement 1 is still not enough without knowing the sign of the square root.

@whyiseveryaliastaken 3 жыл бұрын

@@LamboWalker23 You cannot have something negative in a square root in the first place. What would you square to get to -20? Anything squared is always positive.

@honest_bishop5905 2 жыл бұрын

@@whyiseveryaliastaken only if you are working on reals

@kristinazt3627 4 жыл бұрын

absolutely elegant explanation for Q7, very helpful 🤙🏿

@gmatclub 4 жыл бұрын

Thank you for your feedback! Really appreciate it :-) Please subscribe and always know when we air new GMAT and MBA videos

@Littman31 7 ай бұрын

In question 6, how can we assume that the 300 students is the TOTAL and therefore include students who study neither German or Hindi? There is no information about students not studying any of the mentioned languages in the question statement. I don't see why the total couldn't be 400 for example, with 100 studying neither? That there is 300 in the total becomes apparent when you plug in the 240 studying Hindi (statement 1) and the 60 not studying Hindi (statement 2). Then you can draw the conclusion that there is 0 students studying neither.

@juancarlosgarcia2416 4 жыл бұрын

I think that the question whrere cd>0 1) and 2) are sufficient. From 2) you can compute the values of c or d and you would get 0 and 4 but we should take into account that cd>0 so c and d can't be equal to zero.Hence the answer is c,d=4. Please, let me know if I committed any mistake

@gmatclub 4 жыл бұрын

Hello. You are welcome to post your question/solution here: gmatclub.com/forum/if-x-2-y-2-29-what-is-the-value-of-x-y-2-1-xy-105468.html It is a similar (not the same) question but it will likely get a lot more visibility than comments on KZfaq

@yesayatrisejatikrissetia7869 4 жыл бұрын

Same here. I think it should be D.

@mafimalone1896 4 жыл бұрын

I believe Q2 should be answer B, the (1) just can form to the same as the question gave us. The question is can we get or not get result 4. From (1) we get cd=cd dost not make sense. From (2) we get c=d = 4 / 0 . cd>0 then, c=d=4 , and the we can get to the question get result is 4. (2) is sufficient

@alexisha2241 4 жыл бұрын

This video is amazing! Very helpful!

@gmatclub 4 жыл бұрын

Thank you. Please subscribe to GMAT Club's channel to see more of our videos in your feed and perhaps setup notifications to participate in one of the live sessions. We have them often - please join us.

@LifeofaKrishnaBhakt 6 жыл бұрын

wonderful questions with awesome explanations..really helpful :)

@theavghustler 6 жыл бұрын

Hey, In question 4:- x/y >1 , thus even if y is negative , both their ratio is still greater than 1, to me x must be lil bit greater than y as their ratio is greater than 1.

@shyamss2338 4 жыл бұрын

X is a greater negative number than Y. Example x could be -7 and y could be -4.

@panos4662 3 жыл бұрын

I am actually giving the GRE test, but GMAT Ninja is also a GRE Ninja!

@linazapata6806 5 жыл бұрын

Awesome! you are a really great professor

@aishwaryavaswani7669 2 жыл бұрын

In the first question cant we put the value of d in the equation c^2+d^2=29 and find c then put it in the formula?

@BranDoesThings 3 жыл бұрын

I am confused about question 2. I did the same work you did (breaking down the question stem to be 2c + 2d = cd) Would that not make statement one a tautological statement (aka it doesn't give us any new info, thus insufficient)?

@hemantbafna6877 4 жыл бұрын

Charles is a big fan of popcorns, I read popcorns everywhere in the questions.

@rupaklibra 6 жыл бұрын

Awesome video as usual..

@franciscolanza3121 4 жыл бұрын

Q2 Answer is D... it doesn't matter that c (or d, because they are equal) can have two different values...in fact since we have cd > 0 neither of them can be equal to 0, so there's only one possible value for c ! We always get the same result, so statement (2) is also sufficient

@gmatclub 4 жыл бұрын

Thank you for your question. I think I know where you are coming from. You may be mis-reading Charle's writing. He wrote C^2=4C but in reality that's not a fact/equation we are solving but rather a question, is C squared equal to 4C? If C is 4, then the answer is YES, but if C is 2, then the answer is "NO" that is why Statement 2 is insufficient by itself. You can see a discussion of this question here: gmatclub.com/forum/if-cd-0-does-c-2-d-284999.html (this is a tricky GMAT Club Tests question)

@chaitanyakane6656 2 жыл бұрын

@@gmatclub I have been scratching my head over this thing for a while and it's so simple!!! If there's a question mark in the question stem of a DS statement, we need to carry the question mark as we solve. Here we are given " c=d " in the second case , then the statement becomes " c^2 - 2c = 0 ? " , which is , " c=2 ? " We still have the question mark at the end, implying that we can't be certain of the answer. In first case, we get " cd - 2(c + d) = 0 ", which is " 0=0" after plugging in 2(c+d) = cd , as given in the first statement.

@adarshnb618 Жыл бұрын

In Q1, statement 1, why did we not substitute the value of 'd' in the equation c2 + d2 =29, and get the value of c? By doing this, we will have values for c and d, and hence we find the value of (c+d)2

@gmatclub Жыл бұрын

It's probably better to ask this query to GMAT Ninja on GMAT Club :-)

@shivamagrawal1519 3 жыл бұрын

Awesome lecture

@gmatclub 3 жыл бұрын

Thanks for liking! Do Subscribe to our KZfaq Channel to Get Free 7-day Access to the GMAT Club Tests. kzfaq.info/love/EIeUiExox8otkETZFC9DKA Subscribe and then follow the instructions posted here gmatclub.com/google_verify.php

@user-qj8xd9ee8f 7 ай бұрын

whats the AD/BCE thing?

@prernagahlawat5801 4 жыл бұрын

Hi Charles, Firstly, very insightful videos, thanks for these. Secondly, you started the video mentioning something about the DS basics video, can't really find it. can you please share the link? also, it will be great if you can share the link for all quant basics video that you have done :)

@myhana90 4 жыл бұрын

gmatclub.com/forum/all-gmat-ninja-live-youtube-videos-by-topic-309678.html#p2396353. not sure if you found what you wanted yet but the above link entails not only all quant videos but also verbal videos.

@navinsenthil2296 3 жыл бұрын

is it a steph curry reference for the popcorn question?

@lilylily6316 4 жыл бұрын

I think Q2 is D because statement 2 gives 2 answers : c=d=0 and c=d=4 but c,d cannot be 0 so c=d=4 is sufficient. Am I missing anything?

@gmatclub 4 жыл бұрын

Statement (2) c = d. The question becomes: does (c-2)(c-2) = 4 ? --> does (c - 2)^2 = 4 --> does c = 0 or c = 4. We don't know that, so this statement is not sufficient. To see a more detailed explanation and discussion, please see this link: gmatclub.com/forum/if-cd-0-does-c-2-d-284999.html

@marcodanieletto7222 4 жыл бұрын

@@gmatclub I think LILY is right. We get c=0 or c=4, but since we know that cd>0 we can eliminate the solution c=0. Thus both statement are sufficient. Correct answer is D.

@mafimalone1896 4 жыл бұрын

I believe Q2 should be answer B, the (1) just can form to the same as the question gave us. The question is can we get or not get result 4. From (1) we get cd=cd dost not make sense. From (2) we get c=d = 4 / 0 . And use this to the question , no matter 4 or 0 we get results 4. So only (2) is sufficient.

@zachremland294 4 жыл бұрын

@@marcodanieletto7222 The issue is, you are using the question statement, does (c - 2)^2 = 4 as a fact. From B, the only thing you know is that c = d and cd > 0. With c = d, the question statement is simplified to does (c - 2)^2 = 4? So C, D can equal 8 and cd is > 0, C = D and does not satisfy the equation (c - 2)^2 = 4 . Or C, D = 4 which does satisfy the equation (c - 2)^2 = 4. So you cannot say whether (c - 2)^2 = 4 from the two pieces of information.

@nikky2609 2 жыл бұрын

thanks

@tonyjyoo 4 жыл бұрын

For question 2 - why is it not D? Statement 2 should be only c=4, as the question stem states cd > 0. How can c=0 be a possibility?

@gmatclub 4 жыл бұрын

@vinayakkp7260 4 жыл бұрын

Just curious. In the question about German and Hindi, it is nowhere said that Ames High has only 300 students in total or that German/Hindi are the only two languages offered for study. In that case how can we conclude that Neither German/Hindi is 0?

@myhana90 4 жыл бұрын

Hi Vinayak, it is stated clearly in the first sentence of the question. "at ames high, 300 students study German or Hindi or both". by inference, you can tell there are only 3 scenarios.

@talarchaghlasian7021 3 жыл бұрын

Hi there! Where can i find the answer choices ABCDE ?

@xieo3007 4 жыл бұрын

in Q.9 at 54:12 There is an S3 in the place of a3 in the sequence, and the question doesn't mention S in any part that is why the answer to this question is E

@allwindsouza9595 Жыл бұрын

i guess that was just a typo

@kevinliu9162 3 жыл бұрын

So in the German/Hindi question, studying both German and Hindi doesn't count as studying German? I thought it would be inclusive when first reading the question.. It should clarify that 100 students do not study German alone.

@c6566 3 ай бұрын

Charles, for Q6, how is it implied that nobody studies neither German nor Hindi?? I thought it was a trick question. :(

@gmatclub 3 ай бұрын

Here is the forum link of a similar question (same values & logic but different names). Check Bunuel's explanation for more clarity gmatclub.com/forum/in-jefferson-school-300-students-study-french-or-spanish-or-87885.html

@turgayy.3839 6 жыл бұрын

@gmatclub I somehow cant find the old video, is it on this channel=?

@gmatclub 4 жыл бұрын

Hey There! Found your old comment sorry for a super late reply Yes! :-) For anyone reading now, please try a search or visit one of the Playlists: kzfaq.infoplaylists

@oibre 4 жыл бұрын

@@gmatclub I've looked through the channel and could not find it. Could you pls send us the link? tks!!

@gmatclub 4 жыл бұрын

@@oibre Hi! Here is GMAT NInja's Season 1: kzfaq.info/get/bejne/f85-kq6Glsi3e4k.html Which Video are you looking for?

@chaitanyakane6656 2 жыл бұрын

(might help someone else looking for it right now ) The video Charles is referring to is the second video of this series itself, " Cutting corners kills your GMAT score", where he pointed out some careless mistakes we make while solving DS questions.

@sim5737 2 жыл бұрын

@@chaitanyakane6656 Thank you! This really helped ^^