Dear GMAT Ninja Team, over the last two weeks I went through all of your 18 GMAT Quant Videos. I want to say a big thank you to the whole Team; you did an awesome Job! I decided to watch your videos, because the Quant section really messed up my GMAT Test Practice scores. I don´t know yet whether the videos helped me to improve my score, but I definitely know, that I learned a lot and got to view a ton of questions from a different angle. Thus, for me it was absolutely worth putting the time in the course! Again, thank you so much!!! All the best for you guys!
The way I did q7 was I knew that 4000 would be excluded from the final answer, so I looked in the answers for any set of numbers that was 1 minus the other, in this case 215 and 216 😅
On question 4, why do we not also divide by a further factor of 2 for cases in which N, N appear next to each other (that is to say, one N is somewhere else in the string of six letters but the other two N's are next to each other)? Thank you for making this tutorial, very helpful.
Thank you so much for the kind words! I"m glad that the video helped a bit. I'm not quite sure what you mean by "distribution problems" -- does that just refer to combinations and permutations in general, or something more specific? Either way: any topic area is fair game on the GMAT, regardless of your performance. Yes, if you ultimately hit your goal of scoring 85+ on quant, you'll mostly see difficult quant questions -- but it's possible to see hard questions in any topic area, and it's possible to create easy questions for any topic, too. The best way to think about it: if you're shooting for an elite score, you'll want to be great at everything. Obviously, you won't literally see EVERYTHING in the relatively small sample of 21 quant questions on your actual exam. But anything is fair game, and with lofty goals, you won't want to cut any corners at all. I hope that helps a bit, and thank you again for watching!
Hey Charles, love the videos! I wanted to ask if, for mental clarity, it would be correct to define Combinations as operations where order DOESN'T matter (and therefore we use the formula), and Permutations as operations where order DOES matter (and we use the "slots" technique)... thanks for the help!
Hi, I just want to clarify something regarding the last question. You mentioned that for the digit 7, the same digits can be formed in 9 different ways because there are 10 digits. When we exclude 7, we are left with 9 options. When 7 is in the thousands place, it includes 0 as a valid digit, resulting in 9 ways. However, when 7 is in the middle or at the end, does it not count if 0 is included? If 0 starts the number, it would become a 3-digit number. Shouldn't it be 8 ways then? Specifically, there are 9 ways when 7 is at the beginning, and 8 ways when 7 is not at the beginning (providing we’re excluding 0). That would give us 8 × 3 = 24, in total 24 + 9 = 33 ways for just the digit 7. Am I wrong?🤔
I think you're referring to the part of the solution that Charles labeled #2, but please tell me if I've got that wrong. In this part, Charles specified that he made the thousands digit a 7, this number would have three 7s in it, and there would be a fourth number that would vary. There are nine options for this fourth number (the digits 0-9 but excluding 7), and this fourth number could go in the hundreds, tens, or units spot. In this part of the solution, Charles did not say he'd put this fourth number in the thousands spot. Having done #1 and #2, Charles calculated there are 36 different numbers that would satisfy the "3 digits the same and one digit different" requirement if the number started with a 7. He then asked how many different starting digits could we have? In other words, how many different numbers could replace the 7 in steps #1 and #2? The question tells us that we're only looking for numbers greater than 4000, so Charles said he could have any number from 4-9 occupying the thousands digit. You're absolutely right that if 0 was in the thousands digit, we'd actually have a three-digit number. However, Charles was only looking at numbers that had a 4, 5, 6, 7, 8, or 9 in that digit, so we don't have to worry about what happens if there were a 0 there. I hope that helps!
@@GMATNinjaTutoring hey guys! is there no video for coordinate geometry?? Also I wanted to know what resources we can do with these videos to really cement the concepts covered here and consider ourselves "ready" for a certain topic. Thank you so much for the content!! really really appreciate you guys and the pedagogy you use :)
For q5, how do you proceed after selecting with 3 from a group of 15 ? you said we could work with that method also . Can you pls elaborate ? thanks in advance charles !
Hey Charles @GMAT Ninja Tutoring! for Q5 i used the logic of there being 15 people to choose from and once a person is chosen there cant be a repeat from that country, so first choice we have 15, then 12, then 9. I did 15 x 12 x 9 and then divided by 3! as its a combinations question. I also landed at the correct answer- does that approach make sense or is it just coincidence? Thanks so much! Aman
Yup, that solution works perfectly well, too! Most good GMAT problems have multiple potential solution paths, and I happened to choose a different one for the video, mostly because some students struggle to get their heads around the "combinations adjustment" -- in this case, dividing by 3! to get the final answer. But your method 100% correct here. Nice work, and have fun studying!
Hey Charles, Firstly, like a billion thanks to you and your team for all the effort. And the Rocky joke was hilarious. Just a teensy bit query, for Q5 i figured that answer must be a multiple of 15. And surprisingly there were just two. 2730 couldn't be the answer for obvious reason and got 270 as the answer. Is this approach advisable? It does save time and effort. TIA
I'd love to say you could rely on this approach because it sounds great! How did you know the answer must be a multiple of 15? Unfortunately, it's not a good idea to rely on approaches like this. We don't have the same resources as the folks over at GMAC. Any real exam question goes through multiple rounds of testing and refinement and while we did all we could with the questions in these videos, we just can't match the level of care that goes into producing a real question. We chose the incorrect answers for this question based on the ways we thought someone might go wrong in arriving at an answer. Perhaps we could have swapped out the 2,730 choice for something like 330 or 420 or 540. If we did that, it would probably rule out your approach as a viable method, and it's likely the writers for the real test questions will have the time to think about workarounds like this. I'm sorry I don't have better news, but thank you for your comment and for all your kind words!
thanks for your swift response Charles and apologies for my delayed one. 😅😅 I figured total people would be 15 and then 12 and 9 to choose from. So the solution must be divisible my 15. I’m also a bit skeptical of using this approach due to same reasons you mentioned. What if GMAC decides to be a little sneaky and throw in some close multiples of 15? 😬 And yes, you guys do amazing work at par with GMAC if not more. Cheers
Hi @gmatninja and Charles! Your videos have helped me a lot so thanks for that :D. I have a quick question though, you mentioned at the start that a Q75 to Q80 is a good score for modest goals but that would translate to 32% and 64% percentile respectively which would most likely lead to a score of a low to mid 500's on the GMAT focus (550-600 old one). Did you by any chance mean 75-80 percentile? Asking this because I have been stuck on a low Quant score even though I understand most of the concepts well. Thanks in advance!
For starters, 80 is a remarkably difficult score to achieve on the GMAT quant section, even though it may not sound all that high on a percentile basis. If you're familiar with the old score scale, an 80 on the new GMAT is equivalent to a 49 or 50 on the old scale -- and you have to be really, really good to hit that level, regardless of the percentile. So I'd argue that 80+ is actually a pretty ambitious goal. It might be easy to achieve for some test-takers, and if you're one of those, congratulations! But it's truly a great score. Many test-takers will have a more modest goal, depending on their skills and where they intend to apply for graduate school. A 75Q or even a 70Q will open up plenty of great doors for some applicants, depending on the situation. So when I refer to a "modest" score, I mean it in relative terms -- many applicants don't need a Q80 or a Q85, and for those test-takers, there's no real need to master absolutely everything that we cover in these videos. I hope that helps a bit, and have fun studying!
If the order didn't matter in Q1, you could treat it in the same way Charles does when he finds the number of domestic cities OR the number of international cities a passenger could travel to in Q2. I hope that helps!
Dear GMAT Ninja Team, over the last two weeks I went through all of your 18 GMAT Quant Videos. I want to say a big thank you to the whole Team; you did an awesome Job!
I decided to watch your videos, because the Quant section really messed up my GMAT Test Practice scores. I don´t know yet whether the videos helped me to improve my score, but I definitely know, that I learned a lot and got to view a ton of questions from a different angle. Thus, for me it was absolutely worth putting the time in the course!
Again, thank you so much!!!
All the best for you guys!
The way I did q7 was I knew that 4000 would be excluded from the final answer, so I looked in the answers for any set of numbers that was 1 minus the other, in this case 215 and 216 😅
On question 4, why do we not also divide by a further factor of 2 for cases in which N, N appear next to each other (that is to say, one N is somewhere else in the string of six letters but the other two N's are next to each other)? Thank you for making this tutorial, very helpful.
You are a SAVIOUR Charles
Thank you so much for the kind words! I"m glad that the video helped a bit.
I'm not quite sure what you mean by "distribution problems" -- does that just refer to combinations and permutations in general, or something more specific?
Either way: any topic area is fair game on the GMAT, regardless of your performance. Yes, if you ultimately hit your goal of scoring 85+ on quant, you'll mostly see difficult quant questions -- but it's possible to see hard questions in any topic area, and it's possible to create easy questions for any topic, too.
The best way to think about it: if you're shooting for an elite score, you'll want to be great at everything. Obviously, you won't literally see EVERYTHING in the relatively small sample of 21 quant questions on your actual exam. But anything is fair game, and with lofty goals, you won't want to cut any corners at all.
I hope that helps a bit, and thank you again for watching!
Hey Charles, love the videos! I wanted to ask if, for mental clarity, it would be correct to define Combinations as operations where order DOESN'T matter (and therefore we use the formula), and Permutations as operations where order DOES matter (and we use the "slots" technique)... thanks for the help!
I actually came to a similar conclusion, though there are nuances as he has already shown, it's a good starting logic in my opinion though
Rocky Mountain Oysters joke @29:48 was absolutely hilarious. Thanks for making this video so fun and helpful.
Nothing is funnier than deep-fried testicles, right? Thank you for the kind words, and have fun studying!
Hi, I just want to clarify something regarding the last question. You mentioned that for the digit 7, the same digits can be formed in 9 different ways because there are 10 digits. When we exclude 7, we are left with 9 options.
When 7 is in the thousands place, it includes 0 as a valid digit, resulting in 9 ways. However, when 7 is in the middle or at the end, does it not count if 0 is included? If 0 starts the number, it would become a 3-digit number.
Shouldn't it be 8 ways then? Specifically, there are 9 ways when 7 is at the beginning, and 8 ways when 7 is not at the beginning (providing we’re excluding 0). That would give us 8 × 3 = 24, in total 24 + 9 = 33 ways for just the digit 7. Am I wrong?🤔
I think you're referring to the part of the solution that Charles labeled #2, but please tell me if I've got that wrong. In this part, Charles specified that he made the thousands digit a 7, this number would have three 7s in it, and there would be a fourth number that would vary. There are nine options for this fourth number (the digits 0-9 but excluding 7), and this fourth number could go in the hundreds, tens, or units spot. In this part of the solution, Charles did not say he'd put this fourth number in the thousands spot.
Having done #1 and #2, Charles calculated there are 36 different numbers that would satisfy the "3 digits the same and one digit different" requirement if the number started with a 7. He then asked how many different starting digits could we have? In other words, how many different numbers could replace the 7 in steps #1 and #2? The question tells us that we're only looking for numbers greater than 4000, so Charles said he could have any number from 4-9 occupying the thousands digit.
You're absolutely right that if 0 was in the thousands digit, we'd actually have a three-digit number. However, Charles was only looking at numbers that had a 4, 5, 6, 7, 8, or 9 in that digit, so we don't have to worry about what happens if there were a 0 there.
I hope that helps!
For Q5, I thought of it as 15*12*9/3!. Got 270 as the answer, but not sure if its the right thought process
Yes, that works just fine! I chose to highlight a different path in the video, but your solution is equally valid. Nice work!
Need a video on remainder concepts of number system, thanks for awesome videos❤
Thank you for the kind words! Remainders and related concepts are covered in this video: th-cam.com/video/yXKTkUGzIkg/w-d-xo.html.
@@GMATNinjaTutoring thankyou
@@GMATNinjaTutoring hey guys! is there no video for coordinate geometry?? Also I wanted to know what resources we can do with these videos to really cement the concepts covered here and consider ourselves "ready" for a certain topic. Thank you so much for the content!! really really appreciate you guys and the pedagogy you use :)
@@amanuttam7222 no need for that on the new gmat
For q5, how do you proceed after selecting with 3 from a group of 15 ? you said we could work with that method also . Can you pls elaborate ? thanks in advance charles !
Hey Charles @GMAT Ninja Tutoring! for Q5 i used the logic of there being 15 people to choose from and once a person is chosen there cant be a repeat from that country, so first choice we have 15, then 12, then 9. I did 15 x 12 x 9 and then divided by 3! as its a combinations question. I also landed at the correct answer- does that approach make sense or is it just coincidence?
Thanks so much!
Aman
Yup, that solution works perfectly well, too! Most good GMAT problems have multiple potential solution paths, and I happened to choose a different one for the video, mostly because some students struggle to get their heads around the "combinations adjustment" -- in this case, dividing by 3! to get the final answer. But your method 100% correct here.
Nice work, and have fun studying!
Hey Charles,
Firstly, like a billion thanks to you and your team for all the effort. And the Rocky joke was hilarious.
Just a teensy bit query, for Q5 i figured that answer must be a multiple of 15. And surprisingly there were just two. 2730 couldn't be the answer for obvious reason and got 270 as the answer. Is this approach advisable? It does save time and effort.
TIA
I'd love to say you could rely on this approach because it sounds great! How did you know the answer must be a multiple of 15? Unfortunately, it's not a good idea to rely on approaches like this.
We don't have the same resources as the folks over at GMAC. Any real exam question goes through multiple rounds of testing and refinement and while we did all we could with the questions in these videos, we just can't match the level of care that goes into producing a real question. We chose the incorrect answers for this question based on the ways we thought someone might go wrong in arriving at an answer. Perhaps we could have swapped out the 2,730 choice for something like 330 or 420 or 540. If we did that, it would probably rule out your approach as a viable method, and it's likely the writers for the real test questions will have the time to think about workarounds like this.
I'm sorry I don't have better news, but thank you for your comment and for all your kind words!
thanks for your swift response Charles and apologies for my delayed one. 😅😅
I figured total people would be 15 and then 12 and 9 to choose from.
So the solution must be divisible my 15.
I’m also a bit skeptical of using this approach due to same reasons you mentioned. What if GMAC decides to be a little sneaky and throw in some close multiples of 15? 😬
And yes, you guys do amazing work at par with GMAC if not more.
Cheers
Hi @gmatninja and Charles! Your videos have helped me a lot so thanks for that :D. I have a quick question though, you mentioned at the start that a Q75 to Q80 is a good score for modest goals but that would translate to 32% and 64% percentile respectively which would most likely lead to a score of a low to mid 500's on the GMAT focus (550-600 old one). Did you by any chance mean 75-80 percentile? Asking this because I have been stuck on a low Quant score even though I understand most of the concepts well. Thanks in advance!
For starters, 80 is a remarkably difficult score to achieve on the GMAT quant section, even though it may not sound all that high on a percentile basis. If you're familiar with the old score scale, an 80 on the new GMAT is equivalent to a 49 or 50 on the old scale -- and you have to be really, really good to hit that level, regardless of the percentile.
So I'd argue that 80+ is actually a pretty ambitious goal. It might be easy to achieve for some test-takers, and if you're one of those, congratulations! But it's truly a great score.
Many test-takers will have a more modest goal, depending on their skills and where they intend to apply for graduate school. A 75Q or even a 70Q will open up plenty of great doors for some applicants, depending on the situation. So when I refer to a "modest" score, I mean it in relative terms -- many applicants don't need a Q80 or a Q85, and for those test-takers, there's no real need to master absolutely everything that we cover in these videos.
I hope that helps a bit, and have fun studying!
@@GMATNinjaTutoring Thank you so much for the detailed analysis and setting things in perspective. I really appreciate it :D
if order didnt matter in 1st question, how to approach?
If the order didn't matter in Q1, you could treat it in the same way Charles does when he finds the number of domestic cities OR the number of international cities a passenger could travel to in Q2.
I hope that helps!
Hello, for q4, how do we get a factor of 6? Thanks much
Charles explains where that factor comes from between around 23:00 to around 24:50. Check that out and let us know if you have any other questions!
Could solve the last question under 2 minutes 🎉
🥳
thanks!
❤