Lesson: Introduction to Percent

Comment on Introduction to Percent

In this video, to convert the fraction 3/8 into a percent, you should divide 3 into 8, not 8 into 3. In the video it says you should divide 8 into 3 to get .375, but that is what you will get if you divide 3 into 8.
greenlight-admin's picture

I think you're confusing "divide into" with "divide by"

Consider the fraction 10/2 = 5. We can read this as "ten divided by two equals five" or we can say "two divides into ten five times.

With regard to 3/8. If we were to divide 3 into 8 (as you suggest) then we'd get a number greater than 2, since 3 will divide into 8 over 2 times.

Does that help?

just a curiosity
fraction to percent
1) 9/34
in calculator 900/34 and the answer will come in percent.
what is wrong if you add two zeros in the numerator and divide it by denominator. its 10 times faster isn't it?
greenlight-admin's picture

Sure, but the GRE's online calculator is pretty clunky, and the strategies in this video provide fast solutions.

The last trick is so clever!

How would you convert a fraction where the numbers in the numerator and denominator are bigger than 100?
greenlight-admin's picture

Good question!
An easy approach would be to first divide numerator and denominator by a "nice" value so that they become less than 100, and then apply the technique provided in the video.

For example, let's convert 113/491 to an approximate percent.

First take 113/491 and divide numerator and denominator by 10 to get the EQUIVALENT fraction 11.3/49.1

At this point, we must recognize that if we multiply 49.1 by a number a little bit bigger than 2, we get 100.

So, if we take 11.3/49.1 and multiply top and bottom by a number a little bit bigger than 2, we get (a number a little bigger than 22.6)/100

In other words, 113/491 = 11.3/49.1 = a little more than 22.6%

Does that help?

Yes it definitely helps. Thanks!!

for the official gre question it asks what number BETWEEN 100 and 999 have the same 3 integers. it doesnt say From 100 to 999. so the integers shouldnt include 999 since the question is asking between or before that number.
greenlight-admin's picture

Question link: https://greprepclub.com/forum/what-percent-of-the-integers-between-100-a...

Hmmm, that is unusual phrasing. Typically one would say FROM 100 to 999 INCLUSIVE.
That said, the word "inclusive" means we must include 100 and 999 as well.

Cheers,
Brent

Very useful trick in the last video. Definitely will need to practice this so I don't need the "clunky" calculator during the test.

Thanks for the response.

Best,
Eke
greenlight-admin's picture

By the way, I liked that question so much, I created a new question: https://greprepclub.com/forum/in-a-barrel-full-of-apples-45-of-the-apple...

Cheers,
Brent

You should specify within the fraction column that the fractions are negative. In here, you have (for example) 1/9 = -.111 and -11.1%, but this is false.
greenlight-admin's picture

You're referring to the table that appears at 2:50 in the above video.

The symbol you see in front of some of the decimals and percents isn't a negative symbol (-).
It's actually a tilde symbol (~), which stands for "approximately"

So, for example, even though 1/7 = 0.14285714...., we can say that 1/7 is approximately equal to 0.14

Or we can write: 1/7 = ~0.14

Cheers,
Brent

I have noticed one mistake i make a lot in percent questions is that, when comparing two values to determine how greater one is, vis-a-vis percent, to another, i normally use the wrong denominator. Take this question for example: To the nearest whole percent, the number of drivers who were issued 3 parking tickets is what percent greater to the number of drivers who were issued 4 of more parking tickets." I will just provide the numbers: # for drivers who were just issued 3 tickets is 40 and # of drivers who were issued 4 or more is 36. When solving this, i did: (40-36)/40 * 100 to get 10. But in fact the right arrangement is: 40-36)/36 * 100 to get 11.1. How do i know which value to place in the denominator?
greenlight-admin's picture

Here's a framework for you.

If the question asks "X is what percent greater than Y?". . .
. . . then the answer is (X - Y)/Y * 100

Here, the question asks "To the nearest whole percent, the number of drivers who were issued 3 parking tickets (X) is what percent greater than the number of drivers who were issued 4 of more parking tickets (Y)?"

We can reduce this to: 40 (X) is what percent greater than 36 (Y)?

Does that help?

Cheers,
Brent

Yes, it is helpful.

Thank you!

Thanks for all your help, In the last example, why didn’t we multiple 9 and 34 by a number greater than 2, instead of a number a little bit smaller than 3
greenlight-admin's picture

We want to take the fraction 9/34 and create an equivalent fraction with 100 in the denominator.

34 x 2 = 68, which isn't very close to 100

34 x 3 = 102, which very close to 100.
Since 34 x 3 is a little bit bigger than 100, we need to multiply 34 by a number a little by less than 3 in order to get 100 in the denominator.

Does that help?

Cheers,
Brent

Dear Brent,

Do we ever need to use long division in GRE?

Thanks,
Sajid.
greenlight-admin's picture

Hi Sajid,

I've seen a very very small handful of official questions that require long division (e.g., If N = 17/99, what is the 35th digit to the right of the decimal point of N?).

If your long division skills aren't great, you can always use the GRE's onscreen calculator.

Cheers,
Brent

Hi Brent,
80% of Steph's annual income is from her full-time job.
What fraction of Steph's annual income is from her full-time job?

could you please suggest me someother way because iam bit confused in solving this.

Thank you
greenlight-admin's picture

This question tests your ability to convert percents to fractions.

Saying that "80% of Steph's annual income is from her full-time job" is the same as saying "80/100 of Steph's annual income is from her full-time job"

In other words, "4/5 of Steph's annual income is from her full-time job"

Does that help?

Cheers,
Brent

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