The distribution is
- (1, 1/10), (2, 1/10), (3, 1/10), (4, 1/10), (5, 1/10), (6, 1/10), (7, 1/10), (8, 1/10), (9, 1/10), (10, 1/10)
The expected value is
It is smart to use this gambling machine as the expected value (5.50) is higher than the cost (5.00).