There are 300 seniors at Morse High School, and 50% of them have cars. Of the remaining grades (freshmen, sophomores, and juniors), only 10% of them have cars. If 15% of all the students at Morse have cars, how many students are in the three lower grades? Choose the correct choice from the following choices:
A) 600
B) 900
C) 1200
D) 1600
E) 2100
Let x be the number of students in the lower three grades.   0.1x + 150 = 0.15(x+300)   0.05x = 105   x = 2100   The answer is 2100.
<result>E</result>
There are 300 seniors at Morse High School, and 50% of them have cars. Of the remaining grades (freshmen, sophomores, and juniors), only 10% of them have cars. If 15% of all the students at Morse have cars, how many students are in the three lower grades?