2/5 Of the 200 student in form one of a student are girls how many of them a boy
2/5 of 200 students is (2/5) * 200 = 80.
So, there are 80 girls in the form one class. As there are 200 students in total, the number of boys is 200 - 80 = 120.
Therefore, there are 120 boys in the form one class.