At the beginning of a class, a classroom has 3 empty chairs

[BTGmoderatorAT]

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

Is there a strategic approach to this question? Any experts help please?

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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

[Brent@GMATPrepNow]

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

[Scott@TargetTestPrep]

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

[deloitte247]

Let the total number of students seated initially be 'x' and let the total number of chairs in the classroom be 'n'.
$$n=x+3$$
The three empty chairs were filled by 20% of x
$$therefore,\ 20\%\ of\ x=3$$
or 0.2x=3
x=3/0.2=15
this means that 15 students initially occupied 15 seats and the total number of chairs , n, equals to
n=x+3=15+3=18

option A is correct

[mbawisdom]

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

Is there a strategic approach to this question? Any experts help please?

Total Chairs (TC) = Occupied Chairs (OC) + Unoccupied Chairs (UC)

(1) UC = 3
(2) UC = 0.2*OC

Put UC from (1) into (2):
3 = 0.2*OC
OC = 15

TC = 15 + 3 = 18

[GMATGuruNY]

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 PLUG IN THE ANSWERS, which represent the number of chairs.
Since there are 3 empty chairs at the beginning of class, the original number of students is 3 less than the correct answer choice.
Since the original number of students increases by 20% = 1/5, the original number of students must be a positive MULTIPLE OF 5.
Implication:
When 3 is subtracted from the correct answer choice, the resulting value for the original number of students must be a positive multiple of 5.
Only A works:
18-3 = 15, which is a positive multiple of 5.

The correct answer is A.