Answer:

Step-by-step explanation:
3rd grade:
Number of girls = 16
Number of boys = 15
Total number of students = 31
4th grade:
Number of girls = 15
Number of boys = 18
Total number of students = 33
Formula for probability of an event <em>E</em> can be observed as:

Probability of picking a boy from <em>3rd grade</em>, 
Probability of picking a boy from <em>4th grade</em>, 
These are two independent events of picking a boy from 3rd grade and 4th grade.
So, probability the captain chooses 2 boys in the first pick can be found by multiplying (1) and (2) above.
