GMAT Ninja Quant Ep 8: Number Properties I: Methods & Mechanics

Do you get lost in the “word soup” of GMAT or Executive Assessment number properties questions? Do you some methods for tackling number properties questions, but you're not sure why those methods don't always work?

In this video, Harry -- a GMAT Ninja tutor -- will help you identify which number properties questions can be solved using a methodical, technical approach. Among other things, he'll show you how to use "quasi-algebra" to answer these questions efficiently under time pressure.

This video covers a wide range of difficulty levels. It starts with some simple questions to cover the foundations of GMAT and EA number properties questions, and the difficulty level builds through the rest of the video. This video finishes with a very tough question that will challenge nearly any GMAT or EA test-taker.

This is video #8 in our series of full-length GMAT quant lessons. For updates on upcoming videos, please subscribe!

This video will cover:
➡️ LCM and GCF questions
➡️ Divisibility
➡️ “Quasi-algebra”
➡️ Formalizing the things that can be formalized

This video is for you if:
➡️ You get lost in the “word soup” of number properties questions
➡️ You feel you don’t have a “method” to approach a question
➡️ You have a “method” but you don’t understand why it works

Want more GMAT and EA test-prep tips and advice?

Chapters:
00:00 Introduction
02:55 Question 1 - LCM and GCF
11:58 Question 2 - Is x an integer?
17:22 Question 3 - Divisibility
26:09 Question 4 - Divisor or Multiple?
32:11 Question 5 - Which one is an integer?
40:24 Question 6 - Including factorials
46:56 Question 7 - Make it a multiple
52:12 Question 8 - Raised to the 4th power
59:51 Question 9 - Tables and Divisibility

[aneeshabadhwar]

I usually don't write comments on YouTube, but the series are amazing! Was literally chewing my brain off with quant, you guys are absolute heroes! Thank you!!!

[karimkaan]

I m amazed by how much logics this questions involves instead of pure maths and rules

[livpgcf]

This is amazing, I could solve every exercise but it took me a while. These methods and approach to exercises are easier and faster than everything I knew before.

[anuragmishra]

A great resource for making strong fundamental of number properties topics. Thanks a lot Harry love from India🇮🇳 ❤

[BSA]

for question 8 I came to the same realisation after solving for S and ending up with 2 3 5 t with fraction powers. so I said to myself in order for S to be an integer then these fractions must be eliminated. so 1- each fraction then t^1/4 = 2^1/4 x 3^3/4 x 5^3/4 and raised everything to the power of 4 and got the same result as Harry. It took me 30 minutes to make a sense of it so NGMI on the real GMAT :)

[tbt]

Amazing video! Cleared so many of my doubts and refreshed the basics. Thankyou for that.

[gauravmishra]

I could do the last question but struggled with initial questions, which I think indicates gaps in my conceptual knowledge. Beautiful lesson as always. Thank you.

[wisamey]

If you see an up tick in your views from Saudi Arabia, that would be me!

Great videos. Thanks a lot

[HimanshuSingh-jctk]

QQ: I had also taken the same approach in the penultimate question as explained by Harry. But then later took a detour: No information about variable ‘t’ is given. So let’s say S is 11 so 11 raised to 4 will give us t equal to 11 raised by 4 divided by 120. Since we do not know whether t is an integer or not how do I refrain from my engineering background get in my way of solving such questions.

[TheAmigoBoyz]

For Q6, you could actually just test the options by factoring 26 from the get go. In other words just do the n=13x2(19x18... 'without 13 and 2' +1). Akthough we know that 19 would be in the paranthesis, we also know that adding 1 to a number changes the prime factors to completely different ones (because any subsequent number has no overlapping prime factors), and thus we can definitely say that 19 will not be in that number. I hope it makes sense to anyone struggling on that question.

[artisticsaurabh]

Thanks to your guidance in the initial questions, I could solve the last one. Took about 6 mins though. Not sure if it's worth investing this kind of time during the test.

[joshuaraphaelson]

For question 8, since it isn't stated that T has to be an integer, couldn't T equal 1/120, which would make s=1?

[kartikgosain]

great video gmat ninja!

I just have a doubt in 9th question, in the question line "they also require an identical gap between a table and the wall at the end of the room", i thought it only meant that the gaps between table and wall at either ends of the room are identical and not identical to the gaps between each table.

But when i saw you take those two gaps as same as the gap between each table, i paused the video right there and made the equation myself and was able to solve the question very quickly.

[tiyaandrews]

Hi, for question 9 I'm having trouble with understanding the wording like you've shown. It's said that the gap b/w two tables is 1/3 of the length, and the gap between the table and the wall are identical. I'd assume both the mentioned gaps to be of different lengths; i.e. the gaps in between to be m/3 and the gaps at the end (let's say x) to sum to 2x (identical). Maybe I'm overthinking with how the question's worded.

[alfredoherrera]

About Q2, I think you are wrong, since the first statement is also sufficient.

As you said, the equation is X^2 = 2K

This means that X^2 is an even number because it is twice an integer. For X^2 to be even, X itself must be an even number (since the square of an odd number is odd). Therefore, X is an integrer, so the statement is sufficient. Am I wrong?

[OmarAbolnasr]

In Q8 I think it must be stated or implied in the question stem that t is an integer

[andreamalison]

Thanks for your fantastic work on this serie :)

[ekaterinaz]

Hi! Thank you! For the second question why is statement 1 insufficient? It says x2/2 is an integer therefore x cannot be 7 because (47/2) does not satisfy statement 1? What value of x that satisfies statement 1 would not be an integer? Except.. maybe 1/2🤔? Thanks again!

[frederickkingjnr]

Hello, For question 2, i saw the algebra and all, but the square of a non integer cannot be an integer and no non integer that is squared and divided by 2 can give an integer so shouldn't it be sufficient? This is not merely algebra but a basic impossibility i think

[AkritiKhetawat]

Amazing video! Do you know where I can find resources to read up more about how to solve sums raised to the 4th power? I'm not very clear with that concept