Solution:
As there are 36 students and ratio of boys : girls = 2:1
⇒ Number of boys = 24 & Number of
girls = 12
As Reena’s position is 19 th ,
⇒ There will be 18 students before Reena
and 17 students after Reena.
As there are 13 boys before Reena, also there will be 5 girls before Reena.
Now, the remaining 11 boys will be after Reena and there will be 6 girls after Reena
So, there are 6 girls after Reena in the class.