Let's go through the problem step by step to find the correct answer.
1. Total Tickets Sold:
[tex]\[ \text{Total tickets} = 2000 \][/tex]
2. Neil's Group Tickets:
Neil and 9 of his friends each bought 10 tickets.
[tex]\[ \text{Total tickets bought by Neil's group} = 10 \times 10 = 100 \][/tex]
3. Probability that the Winning Ticket Belongs to Neil's Group:
We are given that the winning ticket indeed belongs to Neil's group. Therefore, the probability calculation involves consideration within Neil's group only.
4. Total Tickets within Neil's Group:
Each person, including Neil, buys 10 tickets. Thus, there are 10 people:
[tex]\[ \text{Total tickets in Neil's group} = 10 \text{ tickets per person} \times 10 \text{ people} = 100 \][/tex]
5. Probability that the Winning Ticket Belongs to Neil:
Within Neil's group, Neil also holds 10 tickets out of the 100 tickets.
[tex]\[ \text{Probability that Neil's tickets win} = \frac{\text{Number of Neil's tickets}}{\text{Total tickets in Neil's group}} = \frac{10}{100} = \frac{1}{10} \][/tex]
Hence, the correct answer is:
\[ \boxed{\frac{1}{10}}
