There are 300 seniors at Morse High School, and 40% of them have cars. Of the remaining grades (freshmen, sophomores, and juniors), only 10% of them have cars. If 20% of all the students at Morse have cars, how many students are in the three lower grades?  Choose the correct choice from the following options:
A) 600  B) 900  C) 1200  D) 1350  E) 1500
Let x be the number of students in the lower three grades.   0.1x + 120 = 0.2(x+300)   0.1x = 60   x = 600   The answer is 600.
<result>A</result>
There are 300 seniors at Morse High School, and 40% of them have cars. Of the remaining grades (freshmen, sophomores, and juniors), only 10% of them have cars. If 20% of all the students at Morse have cars, how many students are in the three lower grades?