Bunuel wrote:
In the fall semester, Mr. Rodriguez’s, Ms. Vangala’s, and Mr. Hollander’s classrooms all have the same number of students and different numbers of computers. At the start of the spring semester, the number of computers in each classroom remains the same, but a group containing a certain number of students moves from Mr. Hollander’s class to Ms. Vangala’s, another group containing the same number of students drops out of Mr. Hollander’s class entirely, a third group containing the same number of students drops out of Mr. Rodriguez’s class, and all other students remain in the same class as in the fall. If there are as many computers as students in Ms. Vangala’s class during the fall semester, if the number of computers in Mr. Hollander’s class is equal to the number of students who drop out of Mr. Rodriguez’s class, and if the number of computers in Mr. Rodriguez’s class is equal to the product of the numbers of computers in Mr. Hollander’s and Ms. Vangala’s classes, is the ratio of computers to students in Mr. Hollander’s class in the spring greater than the ratio of computers to students in Ms. Vangala’s class in the spring?
(1) In the spring, the ratio of computers to students in Mr. Hollander’s and Ms. Vangala’s classes combined is greater than 1 to 6.
(2) If there were a classroom with 3 students and with as many computers as there are students in Ms. Vangala’s class in the spring, the ratio of computers to students in that classroom would be less than the ratio of computers to students in Mr. Rodriguez’s class in the spring.
Let the students be S in each class and the number of computers be R, V and H in Mr. Rodriguez’s, Ms. Vangala’s, and Mr. Hollander’s classrooms .
In the Fall
Number of students : S......S.......S
Number of computers: R......V.......H
Quote:
At the start of the spring semester, the number of computers in each classroom remains the same, but a group containing a certain number of students moves from Mr. Hollander’s class to Ms. Vangala’s, another group containing the same number of students drops out of Mr. Hollander’s class entirely, a third group containing the same number of students drops out of Mr. Rodriguez’s class, and all other students remain in the same class as in the fall
Let the number of students moving out be y.
In the Spring
Number of students : S-y......S+y.......S-2y
Number of computers: R.........V..........H
Quote:
If there are as many computers as students in Ms. Vangala’s class during the fall semester, if the number of computers in Mr. Hollander’s class is equal to the number of students who drop out of Mr. Rodriguez’s class, and if the number of computers in Mr. Rodriguez’s class is equal to the product of the numbers of computers in Mr. Hollander’s and Ms. Vangala’s classes
So, V=S, H=y and R=HV=Sy.
We have to find :
is the ratio of computers to students in Mr. Hollander’s class in the spring greater than the ratio of computers to students in Ms. Vangala’s class in the spring? => \(\frac{H}{S-2y}>\frac{V}{S+y}\)
As V=S and H=y
\(\frac{y}{S-2y}>\frac{S}{S+y}.........Sy+y^2>S^2-2Sy......s^2-y^2<3Sy\)
So, we have to find whether \(s^2-y^2<3Sy\)
(1) In the spring, the ratio of computers to students in Mr. Hollander’s and Ms. Vangala’s classes combined is greater than 1 to 6.
\(\frac{y+S}{2S-y}>\frac{1}{6}.........6y+6S>2S-y......4S>-7y\)
Nothing much.
(2) If there were a classroom with 3 students and with as many computers as there are students in Ms. Vangala’s class in the spring, the ratio of computers to students in that classroom would be less than the ratio of computers to students in Mr. Rodriguez’s class in the spring.
\(\frac{3}{S+y}<\frac{R}{S-y}.........\frac{S+y}{3}<\frac{Sy}{S-y}.........S^2-y^2<3Sy\)
This is exactly what we were finding out.
Sufficient
B