Dialling 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 `1//45` b. `1//90` c. `1//100` d. none of these
A. `1//45`
B. `1//90`
C. `1//100`
D. none of these

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1 Answers

Correct Answer - B
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 favorable, thus, the required probability is `1//90`.

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