I have chosen 1 playing card. what is the probability of being red or red ace?

Answer: 26/52 or 0.5 or 50%

Step-By-Step:

So since there are 52 cards in a deck and half of them are red which does include the red ace that means you have 26/52 probability. The red aces are already including in this half of the deck and sense it is an or statement we do not need to add it back into the probability.