Answer:
The number of teacher who joined the school is 20
Step-by-step explanation:
Teacher : Students = 1 : 16
Number of teachers = 1x
Number of students = 16x
16x = 1600
x = 1600/16
x = 100
Number of teachers at the beginning = 100
Now, after some teachers (let it be y) joining the school,
Teacher : students = 3:40
The number of teacher who joined the school is 20