Karen packs peanut butter sandwiches in her daughter's lunch 2 randomly chosen days of the week. The other 3 school days, she packs a ham sandwich. She packs a piece of cake on one randomly chosen day and cookies the other four days. What is the probability, expressed as a percentage, that Karen packs a ham sandwich and cake on the same day? Let's be accurate as possible.
There are 5 school days in a week, so the probability Karen packs a ham sandwich is 3 / 5 and the probability she packs cake is 1 / 5. Multiply the two probabilities to find the probability both things happen: 3 / 5 * 1 / 5 = 3 / 25. Now divide 3 by 25 and multiply by 100% to express this probability as a percentage: 3 / 25 * 100% = 12%.
The answer: 12.