Can you keep your marbles?

This week’s Riddler classic is a logic problem.

There are four enormous bags of marbles. They are labeled RED, GREEN, BLUE, and ASSORTED. You want to buy two bags of marbles that are not assorted, and you’d settle for some combination of red, green or blue. However, someone switched around the labels on all four bags so that every single bag is incorrectly labeled. You may sample two marbles out of any of the bags, one at a time. Is there a picking strategy that guarantees that you will buy two non-assorted bags?

My solution:
[Show Solution]

4 thoughts on “Can you keep your marbles?”

    1. Picking from the same bag twice will work sometimes, but it is not guaranteed to work. For example, if you pick two marbles from the bag labeled BLUE and you get one red and one green, then you know for sure that this is the assorted bag. But if instead you picked two red marbles, then it’s possible that the bag is full of red marbles, but it is also possible the bag is “assorted” and you just happened to pick two red marbles.

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