A group of pupils from School A, School B and School C collected a total of 5700kg of old newspapers. Each pupil from School A collected 12kg. Each pupil from School B collected 15kg. Each pupil from School C collected 16kg. Given that 1/5 of these pupils were from School A, 1/4 of the remaining pupils were from School B and the rest were from School C, how many pupils were from School C?
so, what do you know? If there are a,b,c students from the schools, then
note that since a = 1/5 of the students, and
b = 1/4 of the rest, b is also 1/5 of the students.
so c = 3/5 of the students. So, c = 3a = 3b
Also, adding up all the weights, we have
12a + 15b + 16c = 5700
12a+15a+16*3a = 5700
75a = 5700
a = 76
so there are 76*3 = 228 students from C