Probability Question 75
Question: Dialing a telephone number an old man forgets the last two digits remembering only that these are different dialled at random. The probability that the number is dialled correctly, is
Options:
A) $ \frac{1}{45} $
B) $ \frac{1}{90} $
C) $ \frac{1}{100} $
D) None of these
Show Answer
Answer:
Correct Answer: B
Solution:
There are 10 digits $ 0,1,2,3,4,5,6,7,8,9. $
The last two digits can be dialled in $ {}^{10}P_2=90 $ ways, out of which only one way is favourable, thus the required probability $ =\frac{1}{90}. $
BETA
