Final answer:
The probability of drawing a spade or a red ace from a standard deck of playing cards, without double-counting the ace of spades, is 7/26.
Step-by-step explanation:
The probability of drawing a spade or a red ace from an ordinary deck of playing cards can be calculated by analyzing the number of favorable outcomes and dividing by the total number of possibilities. A standard deck has 13 spades, and there are 2 red aces (one in hearts and one in diamonds). However, since one does not want to double count the ace of spades (as it is both a spade and a red card), the total number of favorable outcomes is 13 spades + 1 additional red ace for a total of 14. Since there are 52 cards in a deck, the probability is calculated as 14/52, which simplifies to 7/26.
To avoid confusion, it is essential to remember that the ace of spades should not be double-counted since it already falls within the category of spades. Therefore, only the ace of hearts and the ace of diamonds are counted separately when determining the total number of favorable outcomes.