Home » GMAT » What is the probability that only girls will be elected?
Out of a classroom of 6 boys and 4 girls the teacher picks a president for the student board, a vice president and a secretary. What is the probability that only girls will be elected?
A. 8/125.
B. 2/5.
C. 1/30.
D. 1/720.
E. 13/48.
Correct Answer: C
Explanation/Reference:
Explanation:
The basic principle of this question is that one person can’t be elected to more than one part, therefore when picking a person for a job the "inventory" of remaining people is growing smaller. The probability of picking a girl for the first job is 4/10 = 2/5. The probability of picking a girl for the second job is (4-1)/(10-1) = 3/9. The probability of picking a girl for the third job is (3-1)/(9-1) = 1/4. The probability of all three events happening is: 2/5 x 3/9 x ¼ = 1/30.
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