- Video Course
- Video Course Overview
- General GMAT Strategies - 7 videos (free)
- Data Sufficiency - 16 videos (free)
- Arithmetic - 38 videos
- Powers and Roots - 36 videos
- Algebra and Equation Solving - 73 videos
- Word Problems - 48 videos
- Geometry - 42 videos
- Integer Properties - 38 videos
- Statistics - 20 videos
- Counting - 27 videos
- Probability - 23 videos
- Analytical Writing Assessment - 5 videos (free)
- Reading Comprehension - 10 videos (free)
- Critical Reasoning - 38 videos
- Sentence Correction - 70 videos
- Integrated Reasoning - 17 videos

- Study Guide
- About
- Office Hours
- Extras
- Prices

## Comment on

Working with Powers of Ten## In the last example you

-Yvonne

## Yes - precisely.

Yes - precisely.

## Brent,

I have a doubt on the exercise 393 from the O.G. (2017 edition). Could you explain me in a different answer from the OG Answer Explanations, please?

Thank you in advance.

## Sure thing.

Sure thing.

Here's my step-by-step solution: https://gmatclub.com/forum/are-all-of-the-numbers-in-a-certain-list-of-1...

If you have any questions about my solution, don't hesitate to ask.

Cheers,

Brent

## Brent,

Sorry, but I can't see that the Statement 2 is sufficient, why the sum of 3 numbers must be equal? Couldn't I put 3+4+5=12?

Cheers,

Pedro

## You're right about 3 + 4 + 5

You're right about 3 + 4 + 5 = 12, but with that example, we're only dealing with three numbers (and we're told that the list has 15 numbers).

At this point, even if we want to add just one more number to the list, we can see that we end up having problems satisfying the condition that "the sum of ANY 3 numbers in the list is 12".

For example, what happens if we add another 3 to the list to get {3, 3, 4, 5}?

At this point, we cannot say that the sum of ANY 3 numbers in the list is 12. For example, if we choose 3, 3, and 5, the sum of those 3 numbers is NOT 12.

Does that help?

Cheers,

Brent

## Aha! Now it is clear for me!

Thank you very much!

Cheers,

Pedro

## Hi Brent,

Do you have a solution for this question https://gmatclub.com/forum/if-z-is-a-three-digit-positive-integer-what-is-the-value-of-69999.html

I am having a hard time coming up with a method of how to come up with values z=230, z=221, hence cannot fully understand proposed solutions

## Nice question!

Nice question!

Here's my full solution: https://gmatclub.com/forum/if-z-is-a-three-digit-positive-integer-what-i...

Cheers,

Brent