Lesson: Introduction to Decimals

Comment on Introduction to Decimals

Hi Brent

In the Manhattan Prep practice question my thought pattern was similar to what you have provided in your model answer. However, I can’t make sense of the final part;

"If 1.43b5 rounded to the nearest THOUSANDTH = 1.436, then b MUST equal 5
So, x must equal 1.4355, which means 10 - x MUST equal 8.5645
Since we can answer the target question with certainty, statement 2 is SUFFICIENT”

Why MUST B equal 5? Why can’t B equal 6,7,8 or 9?

gmat-admin's picture

Hi Matt,

Question link: https://gmatclub.com/forum/in-the-number-1-4ab5-a-and-b-represent-single...

KEY POINT: 1.43b5 rounded to the nearest THOUSANDTH = 1.436

Let's examine some cases...

If b = 5, the number becomes 1.4355
When we round 1.4355 to the nearest THOUSANDTH, we get 1.436
This MEETS the given condition

If b = 6, the number becomes 1.4365
When we round 1.4365 to the nearest THOUSANDTH, we get 1.437
This does NOT meet the given condition

If b = 7, the number becomes 1.4375
When we round 1.4375 to the nearest THOUSANDTH, we get 1.438
This does NOT meet the given condition

If b = 8, the number becomes 1.4385
When we round 1.4385 to the nearest THOUSANDTH, we get 1.439
This does NOT meet the given condition


So, it must be the case that b = 5

Sir, your videos are amazing. But, are these videos alone sufficient to get a 700 on the gmat?

Please advise sir.
gmat-admin's picture

Absolutely. Our lessons cover all of the concepts and strategies required to achieve a 800 score on the GMAT. Each module (especially the Arithmetic module) begins with the most fundamental/basic concepts, and slowly works towards more advanced topics/techniques.


Hi Brent,

Please consider adding the following time saver to your lessons, as I personally have found it very helpful:
9x0.6 = 9x6/10 = 54/10 = 5.4

Thank you,
gmat-admin's picture

That's a great technique, Ana.
Thanks for sharing!!


Hi Brent,

Wondering of there's a quicker method to solve the below question, I followed a very lengthy process and still got the answer wrong.

gmat-admin's picture

That is a CRAZY hard question! In most students, the best approach is to guess and use your time to answer questions that are much less insane.

That said, here's my full solution: https://gmatclub.com/forum/list-t-consist-of-30-positive-decimals-none-o...


Hey Brent for https://gmatclub.com/forum/there-are-24-different-four-digit-integers-than-can-be-141891.html

I did a different approach. I knew each number would get a spot 6 times (24/4). So the sum of all the numbers multiplied by 6 totaled to 84. Staggered them and added them to get the last 3 digits to be -324
gmat-admin's picture

HI Brent,

If Φ is a digit in the number n and n = 3.Φ6, what is Φ?

(1) When rounded to the nearest tenth n is 3.9
(2) When rounded to the nearest integer n is 4

In the second part, we have only one definite answer right? If I were to round off 3.Φ6 to the nearest integer - n is 4. That means, if we round off 3.96, N= 4. If we were to round off 3.86, rounding off would give us 3.9 not 4.

I am not understanding why the answer A and not D.
gmat-admin's picture

Be careful, 3.9 is not an integer.
The integers are: ...-3, -2, -1, 0, 1, 2, 3, 4....

So if we round 3.86 to the nearest integer, we get 4 (not 3.9)

Here's my full solution: https://gmatclub.com/forum/if-is-a-digit-in-the-number-n-and-n-3-6-what-...

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