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Dialing a telephone number to his daughter an old man forgets the last two digits and dialed at random remembering only that they are different. The probability that the number dialed is correct is
  • a)
    1/10
  • b)
    1/45
  • c)
    1/90
  • d)
    1/135
Correct answer is option 'C'. Can you explain this answer?
Most Upvoted Answer
Dialing a telephone number to his daughter an old man forgets the last...
Total number of ways of selecting a pair of numbers which are different from set (0,1,2,3,...,9)
Now, correct pair is only one. Hence, probability that the number dialed is correct = 1/90
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Dialing a telephone number to his daughter an old man forgets the last...
Solution:

Given: The old man forgets the last two digits of the telephone number and dials at random, remembering only that they are different.

Approach: We need to find the probability that the number dialed is correct. Since the old man remembers that the last two digits are different, there are 90 possible combinations for the last two digits (from 01 to 99).

Calculation:
- Total possible combinations for the last two digits = 90
- Total possible combinations for a telephone number = 100 (from 00 to 99)
The probability that the number dialed is correct = (Number of correct combinations)/(Total possible combinations)
= 90/100
= 9/10
= 1/10
Therefore, the correct answer is option C) 1/90.
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Dialing a telephone number to his daughter an old man forgets the last two digits and dialed at random remembering only that they are different. The probability that the number dialed is correct isa)1/10b)1/45c)1/90d)1/135Correct answer is option 'C'. Can you explain this answer?
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