Total boys = 10 + 7 +10 + 9 = 36
Probability of picking a senior = 9/36 , reduces to 1/4
Total girls = 8 + 11 + 9 + 7 = 35
Probability of picking a senior = 7/35, reduces to 1/5
Probability of picking both multiply the probability of each by each other:
= 1/4 x 1/5 = 1/20
Answer is D.
