From a pack of 52 cards one card is drawn at random. What is the probability that the card drawn is a ten or a spade?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \(\displaystyle\frac{4}{13}\)
For ‘A or B’, count the cards of each kind and take away the cards counted twice: \(P(A\cup B)=P(A)+P(B)-P(A\cap B)\).
Tens: 4 cards; spades: 13 cards
The ten of spades is in both groups, so it is counted once only: \(4+13-1=16\) cards
Probability \(=\displaystyle\frac{16}{52}=\frac{4}{13}\)
Tip: In ‘either-or’ card questions, always look for the card that belongs to both groups and count it only once.