Question: Rugby Players & Chess Players

Comment on Rugby Players & Chess Players

I am confused with this question. 40% of the students play rugby and play chess(can be 40/100). And how about the students who play rugby do not play chase? why does it represent 0.4x? It cannot be 40 like the first sentence??? Could you please explain the questions?

Thank you in advance.
gmat-admin's picture

In the first sentence, we're told that 40% of the ENTIRE school population plays rugby and chess. Since we're saying the ENTIRE school population is 100, we need only calculate 40% of 100.

The second sentence tells us that 40% of the PEOPLE WHO PLAY RUGBY do not play chess. Since we don't know the number of PEOPLE WHO PLAY RUGBY, we cannot make the same sort of quick calculation as we did with the first sentence. Instead, we first let x = the number of PEOPLE WHO PLAY RUGBY. So, if 40% of the PEOPLE WHO PLAY RUGBY (i.e., x) do not play chess, then we know that 0.4x = the number of rugby players who do not play chess.

Does that help?

Yes, it does. Thank you so much for your assistance.

Could you tell me please. I thought that 40% of x is not only the number of students who play Rugby and not play Chess but also the number of students who not play Rugby nor play Chess.
Why do you assume that 40% of x is just the number of students who play rugby and not play Chess.
gmat-admin's picture

There's an important difference in wording.

If I say, "20% of the employees are female AND over 30 years old," then we know that 20% of ALL employees are 30+ year-old females. So, for example, if there are 200 employees, then exactly 40 of them are 30+ year-old females.

If I say, "20% of the female employees are over 30 years old," then we know that 20% of THE FEMALE employees are 30+ years-old. So, for example, if there are 500 employees, and 300 of those employees are female, then we know that there are 60 female employees (since 20% of 300 =60).

The same concept applies to the question in the video.

Thank so much for all the nice you're doing.

A brilliant question!
gmat-admin's picture

Thanks for that!

Since the Double Matrix method wasn't discussed in this chapter before this question came up; will it be ok to solve this using the Venn Diagram method?
gmat-admin's picture

But the Double Matrix method IS discussed in an earlier lesson (video #20 to be precise).

That said, it's fine to use a Venn diagram to solve overlapping sets questions. However, as I mention in the Double Matrix lesson, Venn diagrams can be less effective when dealing with harder questions.

Approximately what level of a question would this be?
gmat-admin's picture

Whenever it's necessary to use variables with a Double Matrix question, the question is typically in the 700+ range.

https://gmatclub.com/forum/m07-183752.html
sir i dont understand bunuel logic of atmost
please explain
gmat-admin's picture

Here's my full solution: https://gmatclub.com/forum/m07-183752-100.html#p2219914

Cheers,
Brent

The questions have a green, orange and red color tags against them. Was just curious if it associates to a certain difficulty range? thanks.
gmat-admin's picture

If you hover your cursor over each colored tag, you'll see that:
GREEN = 350-500 level of difficulty
ORANGE = 510-650 level of difficulty
RED = 660-800 level of difficulty

Cheers, Brent

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