Answer:
3171 × 10^(44) years
Step-by-step explanation:
For each bit, since we are looking how many years of running it is unavoidable that the device produces an output for the second time, the possible integers are from 0 to 9. This is 10 possible integers for each bit.
Thus, total number of possible 64 bit integers = 10^(64) integers
Now, we are told that the device produces random integers at a rate of one billion per second (10^(9) billion per second)
Let's calculate how many it can produce in a year.
1 year = 365 × 24 × 60 × 60 seconds = 31,536,000 seconds
Thus, per year it will produce;
(10^(9) billion per second) × 31,536,000 seconds = 3.1536 × 10^(16)
Thus;
Number of years of running is it unavoidable that the device produces an output for the second time is;
(10^(64))/(3.1536 × 10^(16)) = 3171 × 10^(44) years
⇒ 
⇒ 
