Question

There is a stack of 10 cards, each given a different number from 1 to 10. Suppose we select a card randomly from the stack, replace it, and then randomly select another card. What is the probability that the first card is an odd number and the second card is less than 5?

Answer 1

20% or 1/5.

Explanation:

Out of ten cards, the chance of getting an odd number is of course 50% or 1/2 since half of them are odd and the other half are even. Then the chance of getting a card less than 5, or 1, 2, 3, or 4 is 40% or 2/5. Multiply these together and half of 2/5 is 1/5 so your answer is 1/5 or 20%.