GMAT Ninja Quant Ep 6: Ratios

Do you sometimes get lost when you see a ratios question on the GMAT or the Executive Assessment? Do you know you should use algebra, but don't know exactly where to start?

In this video, Harry -- a GMAT Ninja tutor -- will build your intuitive understanding of ratios so that you can tackle these questions with 100% confidence.

This video is moderate in difficulty, and could be a challenge for GMAT students who are scoring in the 30s or low 40s on the GMAT quant section. We'll cover all of the foundations of GMAT and EA ratios in the first section of the video, and then things will get a little bit tougher toward the end. But if you're already scoring in the high 40s or low 50s on GMAT quant, you might not find this video challenging.

This is video #6 in our series of full-length GMAT quant lessons. For updates on upcoming videos, please subscribe!

This video will cover:
➡️ Basic ratios – what are they?
➡️ Changing the ratio as the situation changes
➡️ Combining and separating ratios
➡️ Triple ratios questions

This video is for you if:
➡️ You struggle to translate ratios questions onto the page
➡️ You don’t know when or how to use algebra
➡️ You’ve got a process but you don’t understand why it works

Want more GMAT test-prep tips and advice?

Chapters:
00:00 Introduction
02:29 Question 1 - Basic Ratios
09:09 Question 2 - Introducing Algebra
13:58 Question 3 - Triple Ratios
20:59 Question 4 - Changing Situations
27:43 Question 5 - Ratios and Inequalities
32:23 Question 6 - Manipulating Ratios
38:52 Question 7 - Percentage Change with Ratios
47:08 Question 8 - Algebra or Intuition?

[rodamaster]

Great video! For Q8 I used pure logic and intuition: Statement 1: ..."is greater for the whole university than for the men"-> lesser for men -> greater for women, so the ratio is greater for women. Statement 2: "fewer than half are men"-> +1/2 are women and "more than half are men" -> less than a half is women -> we divide and the ratio is greater for women.

[santoshinimahadev]

sir, your teaching methods are extremely clear.

[parvindernogi]

I can’t have a third of swimmer, it will be weird floating around the swimming pool 😂😂😂

[jamesbridgetteray]

I am very confused with question 8. You began crossing out A, B, C, and E what are those in reference to?
I am really struggling to understand the w<u<m. I get that the ratio of f:s majors is greater as a whole in the university than as men, but how can to ratio of women f:s be larger than the university f:s, if the university includes, both men and women

[saksrocks]

Hi - Interesting observation in Question 8. If a/b>c/d ; then (a+c)/b+d lies between a/b and c/d.
While I was not initially able to decipher it by intuition, I think we can arrive at the result by assuming a/b>c/d and then adding cd and ab separately to both sides. then c/d<sum of the ratios<a/b. While i will remember the result for future Qs, how did you arrive at the same by intuition?

Is it due to the fact that if ratios are 1/2 and 1/2, then sum of ratios will be 1/2. If we make one ratio>1/2, to keep the ratio constant, we have to make another ratio<1/2 and hence the sum of ratios will always lie between the two ratios?

[thebaratheon]

last question - the number of women can be 0 (there was NO restriction indicating that there must be at least 1 person of each gender in French or Spanish).

in a hypothetical case of 75 total students in French and 25 total students in Spanish, the ratio of F:S for men can be 40:25, and F:S for women can be 10:0.

If this is the case, how can this be compared at all if the ratio for women is undefined?

The answer should be E based on the lack of limitations given in the question stem.

[pranavagarwal]

Awesome explanation to each question! I have a doubt in question 5. Isn't at least translated into inequality as 'greater than or equal to' instead of 'greater than'?

[ashshettyvlogs]

Loved the 8th question. I have a doubt 'in Q5, isnt "atleast" be L/S >= 3/10 instead ?'

[ngoichoixoinuoc]

Q3, I did differently but somehow still comes to the correct answer.
c/h = 1/5 => c= h/5
we have
d/c = 4/3
=> d/ (h/5) =4/3 => d/h = 20/3

[tarynharalson]

Question about #8 -- When you pushed the question, you ended up coming to Fw/Sw > Fm/Sm. Then by the end of statement 1, you ended up with Fw/Sw > Fm/Sm, which matches the question. How is statement 1 alone not sufficient?

[preyanshisingh]

great video.. i had a doubt although in question 8. hypothetically, what if we could say a definitive yes with statement 1 and a definitive no if we went with statement 2. in this case what would be the correct option? A or E?

[TamirKalderon-vo]

Question 7 is very hard...
Also its very annoying i cant see i can cancel R/B...
IT took Me 3 more steos

[ArshdeepSingh-eksu]

hello, just a query in question 5. Supposedly, on solving the value comes out to be 23.8888. Then what are we supposed to choose in that case? 23 or 24?

[tudorsafta]

Quick query for Q4- in the final formula we have (5x-2)/(2x+8) = 3/2 ; my question is why is it equal to 3/2 as if we definitively know there are 3 cars and 2 trucks left? My understanding is the formula should equal 3x/2x. Where am I misunderstanding?

[Xoustus]

Hello Harry, For Q1, why did you divide by 14 and how did you get that answer?

[bonasusan]

Hi @gmatclub in Q 5 they said guards to swimmers ratio must be atleast 3:10, so shouldnt the inequality sign be greater than or equal to?

[justzzzzletgo]

Thank you for the insightful video, I have a question for the 7th problem. Since they had asked for % change, can't I write the eqn directly as Please let me know why this isnt ok if I made a conceptual error. Thank you.

[matthijsmelgers]

@harryduthie First of all, thanks for the video. I have a question about Q7. Could you explain to me why the like terms of R/B cancel out? For some reason my mind can't comprehend it. Thanks in advance.

[jamesbridgetteray]

Why did you cross multiply? Could you explain that step?

[lenal]

Hello ! For question 3 the question says there are 5 times as many cats as hamsters and you wrote C = 5H but wouldn't that translate to H = 5C ?