In a relay race there are five teams A, B, C, D and E. What is the probability that A, B and C are first three to finish (in any order) (Assume that all finishing orders are equally likely)
1/60
1/40
1/30
1/20
1/10
Prob
This topic has expert replies
-
- Legendary Member
- Posts: 752
- Joined: Sun May 17, 2009 11:04 pm
- Location: Tokyo
- Thanked: 81 times
- GMAT Score:680
IMO E
Total number of ways the race ends=5!
for A,B,C to finish first, fix them in the sequence like
A B C D E
D,E can be arranged in 2ways
ABC can be arranges in 3! ways
prob= 2*3!/5!
=1/10
Total number of ways the race ends=5!
for A,B,C to finish first, fix them in the sequence like
A B C D E
D,E can be arranged in 2ways
ABC can be arranges in 3! ways
prob= 2*3!/5!
=1/10
The powers of two are bloody impolite!!
-
- Master | Next Rank: 500 Posts
- Posts: 121
- Joined: Thu Jun 11, 2009 1:16 am
- Thanked: 4 times
- GMAT Score:720
Ans. 1/10
There are 5C3=10 ways to choose a three teams out of five. Choosing ABC is one way among them (particular case) therefore the probability is 1/10
(This is because the order of the teams that finish 1st,2nd,3rd doesnt count)
There are 5C3=10 ways to choose a three teams out of five. Choosing ABC is one way among them (particular case) therefore the probability is 1/10
(This is because the order of the teams that finish 1st,2nd,3rd doesnt count)