Winner Selection Algorithm?

Question

Algorithms

Hello!
Please tell me, suddenly someone knows the algorithm for choosing the winner, corresponding to the following points:
1. Users "donate" rubles. 1 ruble - 1 ticket. The first user threw 5.000r, the second 50r. Accordingly, there will be 5050 tickets in total. And the winning one is selected - 1-5000 - wine user 1, 5001-5050 - wine user two. That is, this is not a roulette, where there are 3 colors, how many users bet
2 should be taken into account. Before the game, some kind of key should be generated so that after the game, users can check whether the game was fair according to some algorithms.
3. It is impossible to predict / decrypt the key outcome

Answer 1

1-5000 - VIN user 1,
5001-5050 - VIN user two.

So far, what I have managed to understand is that user1 has 5000/5050 chances, and user2 has 50/5050 chances.
Why not just randomly take a number in the range from 1 to 5050?

Answer 2

1. Percentage of the total.
2. Input and output data must be available to all participants m1=md5(num1.SECSALT), m2=md5(num2.SECSALT), m3=md5(num3.SECSALT), etc.
Then we form HASH: HASH=md5(m1.m2.m3.SECSALT) after voting, we reveal num1, num2, num3 and SECSALT to all voters and formulas for verification.
3. One-way hash functions.