Answer:
500 goats
Step-by-step explanation:
We know that 50 goats were marked. If they were the only goats in the countryside, there would be a 100% chance that any goats found would be marked. If a total of 100 goats were hanging around, we'd expect a 50% chance (50/100) of counting a marked goat.
But only 15 out of 150 goats were found. Rephrased, 10% of the goats spotted were marked (15/150). The total population must be a number such that the 50 marked goats have a 10% chance of being spotted. A total of 500 goats (50/10%, or 50/0.1) must be present to account for the 10% rate.
