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 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.
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