Problem Solving

Hi ardz24,

We're told that at the beginning of a class, a classroom has 3 empty chairs and all students are seated, no student leaves the classroom and an additional number of students equal to 20% of the number of students already seated enter the class late and fill the empty chairs. We're asked for the total number of CHAIRS in the classroom. This question can be solved in a number of different ways, depending on how you choose to do the 'math' involved. Here's how you can TEST THE ANSWERS.

Based on the answer choices - and the fact that the 3 empty chairs represent just 20% of the students who are ALREADY seated - it's likely that one of the larger values is the correct answer. Let's TEST Answer B first....

Answer B = 15 chairs
IF.... there are 15 total chairs...
15 - 3 = 12 of the chairs are filled
3/12 = 1/4 = 25% of the seats need to be filled. This is TOO HIGH though (it's supposed to be only 20%), so we need to have MORE seats filled. The only way for that to happen is if there were MORE seats to begin with. There's only one answer that matches....

Final Answer: A

GMAT assassins aren't born, they're made,
Rich

ardz24 wrote:At the beginning of a class, a classroom has 3 empty chairs and all students are seated. No student leaves the classroom, and additional students equal to 20 percent of the number of students already seated enter the class late and fill the empty chairs. What is the total number of chairs in the classroom?

(A) 18
(B) 15
(C) 10
(D) 6
(E) 3

Let N = the number of seated students ORIGINALLY in the class

We're told that the LATE student fill the 3 remaining seats.
So, there are 3 LATE students

We're also told that number of LATE students = 20 percent of the number of students already seated
In other words: number of LATE students = 20 percent of N
Or we can write: 3 = 0.2 N
So, N = 3/0.2 = 15

So, ORIGINALLY, there were 15 seated students AND 3 empty chairs

So, TOTAL number of chairs = 15 + 3 = 18

Answer: A

Cheers,
Brent

ardz24 wrote:At the beginning of a class, a classroom has 3 empty chairs and all students are seated. No student leaves the classroom, and additional students equal to 20 percent of the number of students already seated enter the class late and fill the empty chairs. What is the total number of chairs in the classroom?

(A) 18
(B) 15
(C) 10
(D) 6
(E) 3

We can let n = the total number of students who are already seated, and thus:

0.2n = 3

n = 15

So, there are 15 + 3 = 18 total chairs.

Answer: A