Suppose you have a fair coin: this means it has a 50% chance of landing heads up and a 50% chance of landing tails up. Suppose you flip it three times and these flips are independent. What is the probability that it lands heads up, then tails up, then heads up? So the answer is 1/8, or 12.5%.
The fractional equivalent of the repeating decimal would be 15/99 and 0.1515... is a repeating decimal so it doesn't end, but in the shown number is 4 digits.