GMAT Ninja Quant Ep 7: Percentages

Do you struggle to translate a percentages question into algebra on the GMAT or the Executive Assessment? Have you memorized all the formulas and techniques but you're still missing more percentages questions than you'd like?

In this video, Harry -- a GMAT Ninja tutor -- will build your intuitive understanding of percentages so that you can tackle these questions with 100% confidence. In particular, he'll show you how to make fractions your best friend when you answer percentage questions under time pressure.

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 percentages in the first section of the video, and then things will get 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 difficult.

This is video #7 in our series of full-length GMAT quant lessons. For updates on upcoming videos, please subscribe!

This video will cover:
➡️ Translating word problems into “math speak”
➡️ Single or multiple percentage changes
➡️ How to make fractions your friend in percentages questions
➡️ Compound interest

This video is for you if:
➡️ You get confused by the phrasing of percentages questions
➡️ You’ve memorized the formulas but still miss a frustrating number of questions
➡️ The “tricks” you’ve learned sometimes fall apart during the GMAT or Executive Assessment
➡️ You “know” everything but still struggle

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

Chapters:
00:00 Introduction
03:52 Question 1 - Basic Percentages
11:15 Question 2 - Percentage Change
19:13 Question 3 - "Percentage higher" or "Percentage of"?
26:40 Question 4 - Find the Formula
32:54 Question 5 - Mind the Variables
38:44 Question 6 - Multiple Percentage Changes
46:49 Question 7 - Simple and Compound Interest
56:01 Question 8 - Losing a Fixed Percentage
1:03:24 Question 9 - Annual Rates of Interest

[thesurferontheside]

Trying so much to 1)read twice, 2)be flexible and see the different ways of solving and chose the most efficient, 3)check my work as I go, 4)reread the question actively, BUT I TAKE SO MUCH TIME, like, I just finsihed doing the second step when Harry interrupts us to solve the question. I would probably solve each question in more than 4mn and many questions in my practice are longer than 6mn. I can't beleive how slow I am

[imthebest]

This is amazing Harry. Your explanations are top notch. Thank you so much !

[KeyserTheRedBeard]

impressive video GMAT Ninja Tutoring. I broke that thumbs up on your video. Maintain up the very good work.

[meghasrinivas]

This helped a lot!! Thank you so much Harry!

[radyahhassan]

Thank you so much, Harry! I just have a quick question. For question 8, instead of writing (1-p/100), I rewrote it as (1-p) for ease of calculation since none of the answer choices had p in them, and I actually have the habit of doing lengthier calculations when I do percent calculations. For instance, I isolated p and used its value in b(1-p) as its my default way of thinking. So, with the 100 in there, it would've made my calculations tedious (where I'll multiply and then take 100 common, etc.)

So, in questions like these, is it okay to just write the variable down without 100 in the denominator?

Also, can you provide suggestions on how to do percent questions more efficiently? Using algebraic method usually takes me over 5 mins to solve, so I resorted to plugging in values to shorten my time. Since you mentioned it's not useful, how else can I improve my efficiency?

[ashishsinha]

The penultimate question was extremely tough (for me)

[GG-Faithandlove]

One question
How did you know the last question required a compound interest?

[sparshsinghal]

Heads up for those doing question 3, don't make the same mistake I did

NOTE: If A is 25% greater than B, then A=1.25B, but that does not mean B is 25% less than A. If you said B was 25% less than A, in that instance, B=0.75A, and if you said A is 25% greater than B, then B would be 0.8A=B, and 0.75A is NOT equal to 0.8A

[agasthyathalakala]

Hi Harry, thanks for these video series been a massive help. I'm slightly confused with the last question, i assumed they wanted us to annualize the last quarter growth rate? by assuming 300*4 and using 9600 aren't we using a simple interest i.e 300k growth every quarter? My question is basically this if the compounded growth in the last quarter is 300k, shouldn't each quarter prior be lower? isn't that how compounding works. Do let me know what you think

[karimkaan]

Great insights and explanation as always

[paulcieri]

Hi Harry, for Question 4, couldn’t it be confusing that we don’t know how many hours the firm worked each year? The question doesn’t directly state that the hours were unchanged. Now I know that since it was a problem solving question and not data sufficiency the answer could be found, but how can we be certain that the revenues aren’t an even bigger percentage different if we don’t know that the hours are the same?

[glenchezzie]

Hi Harry, worked Q3 all the way but could not figure out the where the 11 came from. Please help. Thanks

[KLEAKULE]

i just started studying for the gmat and i'm currently using those videos since harry is so good. to understand a bit my situation.. are those exercises considered easy or hard compared to the possibile question on the gmat?

[DanialBhasin]

Hi Harry,
The last part of Q9 feels a little convoluted.
Couldn't we rather use the info we find (Q1=300) as
9, 600*x/100*3/12=300
giving us, 24x=300 which is x=300/24
Leaving us with x=12.5 or 12 1/2.

Just thought this was a easier method
Essentially, its the same, you just did the 300*4 separately.
Just that the method of getting there feels a little confusing, to me at least.

[mohdshijas]

Hi Harry,
great video and explanation but I have a doubt regarding Q8. We got (1-p/100) ^ 3 = b/a. Isn't that the answer ?

[kopaltyagi]

Hi Harry,
Q8 -
I am a little confused with the wordings used in the question here. Because the car loses a certain part of its value each year should it not start losing its value right from the first year - provided the car was worth a dollar on 01st Jan 2019.

Consequently -
Assuming that the car is losing its value each year, then shouldn't the value on 31st December 2019 be A(1-p%) and then Dec 2020 till be A(1-p%) ^2 and so on?

[anvayjoshi]

Hi Harry,

In Q6 at 45:07, how did you equate by increasing the value by a third with 4/3? We have to increase the value by 33 1/3 right? 33% equates to 1/3 with additional 1/3.

Will you please clarify?

Thanks.

[pierof]

Hi, do you have any suggestions to calculate, without memorizing them, the conversion between % and fractions? e.g., 12, 5% --> 1/8

[gianniniolu]

Do we know what the approximate level of question 9? It seems like even knowing the exact method with which to solve this problem would lead to more than 2 min.

[nikitasingh]

For the last question, can we simply try solving what percent of 9.6m gives 300k users? And then multiply that rate by 4? I got the same answer doing so