Lesson: Working with Percent

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Should we learn both ways or the first method is sufficient for gmat
gmat-admin's picture

Make sure you are familiar with all of the ways to express percents.

I am having a lot of trouble recognizing the percent - part - and whole. I continuously put the values in the wrong spots.
gmat-admin's picture

For the Townville question. I wrote 120/800 = x/100, then divided 800 by 8 to get the denom of 100, and 120 by the same 8 to get the numerator of 15, getting 15/100, yielding the same answer. Would you say this is a valid, timely way to solving similar problems using this method?
gmat-admin's picture

Your approach is perfect! In fact, later in the module, we discuss this exact same approach.

For others reading this, here's what kingerikclusters did:

Take: 120/800
Divide top and bottom by 8 to get the EQUIVALENT fraction 15/100, which equals 15% (done!)

This is the fastest/easiest approach, whereas some (many) students will resort to long division to calculate 120 ÷ 800 = 0.15, which equals 15%

Nice work!


Hi Brent,

I did not understand the second part of this answer. Grateful for more clarifiactions please.

If x is 8/3 percent of y, y is what percent of x?

A. 3/8
B. 37.5
C. 375
D. 3,750
E. 3.75
x is 8/3 percent of y
Let's plug in some nice values for x and y that satisfy the above conditions.
We know that 8/3 is 8/3 percent of 100.
So, x = 8/3 and y = 100 works

y is what percent of x?
In other words, 100 is what percent of 8/3?
Rewrite as 100 is what percent of 2 2/3?
Well, 100 is about 40 TIMES 2 2/3
If we express 40 as a percent we get 4000%
So, our answer will be close to 4000
gmat-admin's picture

Question link: https://www.beatthegmat.com/if-x-is-8-3-percent-of-y-y-is-what-percent-o...

Here's another way to look at it.

We can see that 8/3 and y = 100 satisfies the condition that x is 8/3 percent of y.

The question asks "y is what percent of x?"

In other words, "100 is what percent of 8/3?"

Or we can ask "100 is what percent of 2.7?" (since 8/3 ≈ 2.7)

Well, we know that 2.7 is 100% of 2.7

So, 27 is 1,000% of 2.7

And 270 is 10,000% of 2.7

Since 100 lies between 27 and 270, we know that the correct answer is between 1,000% and 10,000%

Answer: D

Does that help?


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