Brain Teasers · Red and Black Cards
Red and Black Card Pairs Puzzle - Play It
Pairs of cards are turned over: black pairs to the dealer, red pairs to you. What are your odds of ending ahead?
What is the red and black cards puzzle?
It looks like a probability question but it is a counting question. The deck's colour totals fix the outcome before the shuffle.
With r red pairs, b black pairs and m mixed pairs, 2r + m = 26 and 2b + m = 26, so r = b.
How it works
A dealer turns over a 52-card deck two cards at a time. Two blacks go to the dealer, two reds to you, and mixed pairs are thrown away. The story asks the probability you end with more cards. You type your answer and check it. Then you step through the answer and the breakdown.
How scoring works
This teaser checks your answer. Any correct form counts - a fraction, a decimal rounded correctly, a percent, or the number in words. You get two tries before the answer opens. A correct first try earns a ticket; a second try or opening the answer early is recorded but earns nothing. The story teasers share one lifetime unlock for free users.
The key insight
Every red card is in a red pair or a mixed pair, and the same for black. Both colours have 26 cards, so you and the dealer always win the same number of pairs. The probability is 0.
The full step-by-step solution lives at /brain-teasers/red-and-black-cards/solution.
A worked example
Suppose 6 mixed pairs come up. Then 2r + 6 = 26 and 2b + 6 = 26, so you and the dealer each win 10 pairs - 20 cards apiece.
Common mistakes
• Answering 50% because the game looks symmetric.
• Trying to simulate the shuffle instead of counting colours.
• Assuming a lucky shuffle could put you ahead.
Why interviews test this
It checks whether you write down the counts before quoting a probability. The written solution is at /brain-teasers/red-and-black-cards/solution.
Play Red and Black Cards on Outcry
Red and Black Cards is free to play on Outcry, in the Brain Teasers section, and every run is timed and scored. Read the guide once, then play Red and Black Cards and check your score against the strategy above. The guide book has a written guide for every other game, and the practice hub and mock assessments put the same skills under a real screen's clock.