Question: Three numbers are chosen from 1 to 8. Find the probability for the 3 chosen numbers to be consecutive.
Options:
A) $ \frac{11}{28} $
B) $ \frac{3}{28} $
C) $ \frac{5}{28} $
D) $ \frac{9}{28} $
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Answer:
Correct Answer: B
Solution:
- The total number of ways of choosing 3 number out of $ 8={}^{8}C _3 $ way
Let E be the event of the three numbers to b consecutive
$ E={(1,2,3), $ $ (2,3,4), $ $ (3,4,5), $ $ (4,5,6), $ $ (5,6,7), $ $ (6,7,8)} $
$ \therefore $ $ P(E)=\frac{n(E)}{n(S)}=\frac{6}{{}^{8}C _3}=\frac{6}{56}=\frac{3}{28} $