Quant Question of the Day Chat

I’ll be honest. And to the moderators dw , this will be my last personal msg in this group.
But if it wasn’t for GMAT Club, I would have quit this long back. Its been a frustratingly lonely journey for me as a Malaysian. Which is why I am very active hsre. It motivates me through my burn out/self doubt phase.

Please restrict the discussion to quantitative topics only. Any non-quantitative posts will be removed. Thank you!

Sure. Pls accept my apologies. Next time it won’t be repeated.

can anyone tell me how to avoid C trap in questions like these- in-a-rectangular-coordinate-system-what-are-the-coordinates-of-point-414310.html#p3334202

added a reply there only but thought of asking you guys for faster response

This is what you have written and asked in doubt column. "once I got the value of x- I presumed we can get the value of y ": This is probably the biggest mistake in GMAT- To assume something, which is not given. Never ever assume anything in GMAT unless it’s given. Keep the emotions aside and let simple math win you a good GMAT score

Note: These types of questions are not answered here. You have to learn it yourself.

I think the variables which can take both positive and negative values of x and y need to be always checked for both values.
But values for things which can’t take a negative value. Like number of objects or time taken you can avoid. But even then with a quadratic equation there are cases where both values are positive in which case E(you can’t find a definite answer) would be the answer and both values are positive but due to some constraint one of them can’t exist, you can find a definite answer

I also find quick sketches very useful:

With statement (1), point C can be anywhere on the green circle, and with statement (2), it can be anywhere on the purple circle. These circles intersect at two points, indicating that point C could be located at either of them. These possible locations are marked in orange on the image above.

I consistently perform well in the quantitative section with scores ranging from 50 to 51. However, I face significant challenges in the verbal section during exams. Despite having strong verbal skills that should enable me to score 32 or above, I find myself struggling to concentrate on the questions. During the exam, I tend to just read the questions without thoroughly analyzing them. I often get distracted, thinking about unrelated things, and end up with scores in the range of 20 to 25. My upcoming exam is just a week away, and I urgently need assistance to overcome these issues and improve my performance in the verbal section. Can someone please provide guidance or tips?

Please help someone

1. SC modifiers
2. SC parallelism
3. CR boldface - teaches you the diff between argument, concl, assumption and premises
4. CR types of flaws

The 4 topics above cover 80% of your score

Watch any YouTube video for these. Roughly an hour each I guess

every thing is clear even when i solve question sapratly I can solve them easily


any LINK ?

any works


They teach you the diff between options sounding right in your head vs logically eliminating every option. Even if you get distracted, you can always rely on the latter

Hello guys can you help me with this DS question

What is SD of given set of numbers whose average is 5?
1. None of the numbers are greater than this Average
2. The Standard deviation is 5 when value of each of the given number is increased by 7
will be grateful if you can provide examples.
to me B is the correct options.
but i seem not to understand the statement 1

In S1, it says all the numbers in set are less than or equal to 5..In this case, SD=0 because each number is exactly at the average or below, so there’s no variation.

If the avg is 5 and none of the numbers is more than 5 then all the numbers have to be 5 because if any number is less than 5(say 3 which is 2 less than 5) we need another number 7(which is 2 more than 5) to maintain the avg of 5

since we don’t have any number greater than 5, it means that all the numbers are exactly 5

You've copied the second statement incorrectly. Here is a correct version:

What is SD of given set of numbers whose average is 5?

(1) None of the numbers are greater than this Average
(2) The Standard deviation is 0 when value of each of the given number is increased by 7

Standard deviation shows how much variation there is from the mean. A low standard deviation indicates that the data points tend to be very close to the mean, whereas a high standard deviation indicates that the data are spread out over a large range of values.

We need to know a couple of important properties for this question:

If we add or subtract a constant to each term in a set:

• The mean will increase or decrease by the same constant.
• The standard deviation (SD) will not change.

If we increase or decrease each term in a set by the same percentage (multiply all terms by the same constant):

• The mean will increase or decrease by the same percentage.
• The SD will increase or decrease by the same percentage.

You can try it yourself:
The SD of a set: {1,1,4} will be the same as that of {5,5,8}, as the second set is obtained by adding 4 to each term of the first set.

This is because the standard deviation shows how much variation there is from the mean. And when adding or subtracting a constant to each term, we are shifting the mean of the set by this constant (the mean will increase or decrease by the same constant), but the variation from the mean remains the same, as all terms are also shifted by the same constant.

Also: If the range or SD of a list is 0, then the list will contain all identical elements. Conversely, if a list contains all identical elements, then the range and SD of the list is 0. If the list contains 1 element: The range is zero and the SD is zero.

This is because if a list contains all identical elements, then there is no variation from the mean, hence SD=0.

BACK TO THE ORIGINAL QUESTION:

What is SD of given set of numbers whose average is 5?


(1) None of the numbers are greater than this Average

If no number is more than the mean, then no number is less than the mean, which implies that this list contains all identical elements (or, equivalently, just one element), so SD=0. Sufficient.

(2) The Standard deviation is 0 when value of each of the given number is increased by 7 -->

If we add or subtract a constant to each term in a set, the SD will not change, so SD=0. Sufficient.

Answer: D.

For more on Standard Deviation check:

https://gmatclub.com/forum/math-standard-deviation-87905.html
https://gmatclub.com/forum/ps-questions ... 85897.html
https://gmatclub.com/forum/ds-questions ... 85896.html

Hope it helps.

P.S. The original question is discussed here: https://gmatclub.com/forum/what-is-sd-o ... 04000.html