SAT Question of the day #3

By 7:00 P.M., 1/3 of the junior class had arrived at
a school dance. By 8:00 P.M., 30 more juniors had
arrived, raising attendance to 1/2 of the junior class.
How many people are in the junior class?
(A) 30
(B) 90
(C) 120
(D) 180
(E) 240

The answer is D.  To view the video explanation click here!