In this video, around 8:00, it is stated that if a spade is removed from a deck of cards, the probability of picking an ace stays the same.
I don't understand why. I tried to simplify with three cards: a red ace, a black ace, and a black ten. (After removing a black card, what is the probability of picking an ace? Before that, it's 2/3.)
1) Remove (black) ten. Two aces remain -> probability 1 2) Remove (black) ace. One ace remains -> probability 0.5
So how does that add up to 2/3? Half the time I get an ace, and half the time I have a 50% chance of getting one. Feels like 0.75, although I am somewhat new to probability.