3. In Dewey Elementary School, there are two
second-grade classes: class A has 35 students
and class B has 45 students. If 40% of the
students in class A walk to school, and 80%
of the students in class B walk to school, what
percent of all the students in the second grade
at Dewey Elementary walk to school?
A) 40%
B) 42.5%
C) 60%
D) 62.5%