Cincinnati Reds First-Place Elimination Scenario
Cincinnati must win 21 more games (50 total) to avoid elimination from first place.
Here are the final standings in a scenario in which Cincinnati finishes in first place with 50 wins:

Team             W	L	PCT	GB
Cincinnati       50	112	0.309	0.00
Milwaukee        50	112	0.309	0.00
Pittsburgh       49	113	0.302	1.00
St. Louis        49	113	0.302	1.00
Chicago          49	113	0.302	1.00

Tie breakers
Cincinnati wins the series with Milwaukee 13 games to 0

To construct the scenario, we start with the current standings in the division:
Team             W	L	GL	PCT	GB
Milwaukee        34	21	107	0.618	0.0
Chicago          32	27	103	0.542	4.0
St. Louis        30	26	106	0.536	4.5
Pittsburgh       31	28	103	0.525	5.0
Cincinnati       29	28	105	0.509	6.0

Next, we show how the remaining series of games plays out in the scenario:

Chicago currently has 4 win(s) against Cincinnati and 0 loss(es).
Chicago wins 9 additional game(s) against Cincinnati and loses 0.
Chicago wins the series 13 games to 0.
Chicago wins 0 additional game(s) against teams outside the division and loses 67.

Chicago currently has 0 win(s) against Milwaukee and 3 loss(es).
Chicago wins 6 additional game(s) against Milwaukee and loses 4.
Chicago loses the series 6 games to 7.
Chicago wins 0 additional game(s) against teams outside the division and loses 67.

Chicago currently has 3 win(s) against Pittsburgh and 4 loss(es).
Chicago wins 1 additional game(s) against Pittsburgh and loses 5.
Chicago loses the series 4 games to 9.
Chicago wins 0 additional game(s) against teams outside the division and loses 67.

Chicago currently has 1 win(s) against St. Louis and 1 loss(es).
Chicago wins 1 additional game(s) against St. Louis and loses 10.
Chicago loses the series 2 games to 11.
Chicago wins 0 additional game(s) against teams outside the division and loses 67.

Cincinnati currently has 0 win(s) against Milwaukee and 0 loss(es).
Cincinnati wins 13 additional game(s) against Milwaukee and loses 0.
Cincinnati wins the series 13 games to 0.
Cincinnati wins 0 additional game(s) against teams outside the division and loses 65.

Cincinnati currently has 1 win(s) against Pittsburgh and 5 loss(es).
Cincinnati wins 3 additional game(s) against Pittsburgh and loses 4.
Cincinnati loses the series 4 games to 9.
Cincinnati wins 0 additional game(s) against teams outside the division and loses 65.

Cincinnati currently has 1 win(s) against St. Louis and 1 loss(es).
Cincinnati wins 5 additional game(s) against St. Louis and loses 6.
Cincinnati loses the series 6 games to 7.
Cincinnati wins 0 additional game(s) against teams outside the division and loses 65.

Milwaukee currently has 1 win(s) against Pittsburgh and 2 loss(es).
Milwaukee wins 7 additional game(s) against Pittsburgh and loses 3.
Milwaukee wins the series 8 games to 5.
Milwaukee wins 0 additional game(s) against teams outside the division and loses 66.

Milwaukee currently has 4 win(s) against St. Louis and 1 loss(es).
Milwaukee wins 5 additional game(s) against St. Louis and loses 3.
Milwaukee wins the series 9 games to 4.
Milwaukee wins 0 additional game(s) against teams outside the division and loses 66.

Pittsburgh currently has 2 win(s) against St. Louis and 5 loss(es).
Pittsburgh wins 6 additional game(s) against St. Louis and loses 0.
Pittsburgh wins the series 8 games to 5.
Pittsburgh wins 0 additional game(s) against teams outside the division and loses 74.

# Cincinnati Reds' magic number
# Cincinnati's magic number
# Reds' magic number
# MLB Playoff Race