Lesson: QC Strategy - Number Sense

Comment on QC Strategy - Number Sense

It's like you guys created

It's like you guys created the GRE and are just spilling all the secrets to beat it! Oh, If I had only found these videos earlier! T___T

I seceond that!

I multiplied (2x-6)/5 by 10

I multiplied (2x-6)/5 by 10 and got 2x-12. Where is the 4x coming from? (2x - 6)/5 TIMES 10 = 10(2x -

(2x - 6)/5 TIMES 10 = 10(2x - 6)/5

= 2(2x - 6)/1

= 2(2x - 6)

= 4x - 12

incredible math gre lessons

incredible math gre lessons

The number sense technique is

The number sense technique is sweet. But needs practice. You can solve numbers in seconds. what if we apply x=-4. Then A

what if we apply x=-4. Then A must be negative , B must be positive. How could you say A is greater? You're referring to the

You're referring to the question that starts at 0:20 in the above video.

Your point would be true IF x could equal -4. However, the given condition (x > 3) states that x must be greater than 3.

On the last GRE question I

On the last GRE question I don't understand how you were able to expand to the following.
Expand each to get:
Quantity A: (40075)(90042) + 90042
Quantity B: (40075)(90042) + 40075 I'm happy to help.

I'm happy to help.

We started with:
Quantity A: (40076)(90042)
Quantity B: (40075)(90043)

I wanted to get these two quantities to look more alike (since they're easier to compare when they share certain values)

We can rewrite 40076 as (40075 + 1), and rewrite 90043 as (90042 + 1) to get:
Quantity A: (40075 + 1)(90042)
Quantity B: (40075)(90042 + 1)

Notice that each quantity now has 40075, and each quantity now has 90042

Expand each to get:
Quantity A: (40075)(90042) + 90042
Quantity B: (40075)(90042) + 40075

----------ASIDE---------------------
For quantity A, we can think of it this way:
(40075 + 1)(90042) = (90042)(40075 + 1)
From here, we can use the distributive property to multiply these values.

In general, the distributive property says x(y + z) = xy + xy
For example: 5(2 + 6) = (5)(2) + (5)(6)
And 3(x + 1) = 3x + 3
Likewise, (90042)(40075 + 1) = (40075)(90042) + 90042

And, for quantity B, (40075)(90042 + 1) = (40075)(90042) + 40075

For more on the distributive property, you can watch: https://www.greenlighttestprep.com/module/gre-arithmetic/video/1057 (starting at 4:07)

Also, you can watch this one on expanding expressions: https://www.greenlighttestprep.com/module/gre-algebra-and-equation-solvi...
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Please let me know if that helps clear things up.

Cheers,
Brent

Hello i didn't got the

Hello I didn't get the concept of (2x-6)/5 and (2-x)/2 can you explain me the multiplication of 10? You're referring to 0:54 in

You're referring to 0:54 in the video.

In order to eliminate both fractions, we can multiply both values by the least common multiple (LCM) of the two denominators. Here, the denominators are 5 and 2, so the LCM is 10.

Notice that something nice happens when we multiply both quantities by 10.

Given:
QUANTITY A: (2x - 6)/5
QUANTITY B: (2 - x)/2

Multiply both quantities by 10 to get:
QUANTITY A: 10(2x - 6)/5
QUANTITY B: 10(2 - x)/2

We can rewrite both values as follows:
QUANTITY A: (2x - 6)(10/5)
QUANTITY B: (2 - x)(10/2)

Simplify the fractions to get:
QUANTITY A: (2x - 6)(2)
QUANTITY B: (2 - x)(5)

Expand each quantity:
QUANTITY A: 4x - 12
QUANTITY B: 10 - 5x

Does that help?

For more on the above strategy, watch: https://gmatclub.com/forum/if-x-and-y-are-positive-numbers-is-x-1-y-1-x-...