Answer:
More than 5 times
Step-by-step explanation:
There are 10 options for the last digit (0, 1, 2.....9)
Probof 0.5 means 50% chance of getting it right,
Which would happen when he has tried 50% of the total possibilities, which are 10
50% of 10 = 5
He'll have to dial 5 times for a probability of 0.5.
More than 5 times for a probability of more than 0.5
