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 20% of all the students at Morse have cars, how many students are in the three lower grades?  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 + 150 = 0.2(x+300)   0.1x = 900   x = 900   The answer is 900.
<result>B</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 20% of all the students at Morse have cars, how many students are in the three lower grades?