median plover
Please help me figure out which part I did wrong
Problem:
A high school consists of 3 grades
Grade 12: 5 students
Grade 11: 4 students
Grade 10: 3 students
Randomly choose 4 students of the school to form a team. Calculate the probability of getting a team with no more than 2 grades
My solution:
P = P(no grade 12) + P(no grade 11) + P(no grade 10)
n(no grade 12) = (4+3)C4 = 35
n(no 11) = (5+3)C4 = 70
n(no 10) = (5+4)C4 = 126
=> P = (35+70+126) / (5+4+3)C4 = 7/15
The correct answer is 5/11
vernal breach