A spy leaves a message using three colored buttons: Red, Blue, and Green. The message must follow three rules: 1) The Red button cannot be placed immediately next to the Blue button. 2) The Green button must be placed somewhere to the right of the Red button. 3) Exactly three buttons are pressed in a sequence. What is the only valid sequence of buttons from left to right?
Red, Green, Blue
Rule 2 states Green is to the right of Red, so Red cannot be last and Green cannot be first. Thus, Red must be first or second, and Green must be second or third. If Red is first, Green is either second or third. Let's test Red, Green, Blue: Red is not next to Blue (separated by Green), Green is to the right of Red, and there are three buttons. This satisfies all rules. (If Red, Blue, Green: Red is next to Blue, violating Rule 1).
About this riddle
Logic riddles give you a few facts and ask what must be true. List what you know, cross out what cannot be, and see what is left.
Difficulty: Medium. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
More logic riddles
You have 9 coins that look identical, but one is counterfeit and weighs slightly less than the rest. Using a balance scale, what is the minimum number of weighings needed to guarantee finding the fake coin?
Five identical boxes are lined up in a row. A prize is hidden in one of them. Box A says 'The prize is in Box B or C.' Box B says 'The prize is in an even-numbered box.' Box C says 'The prize is in Box A.' Box D says 'The prize is in Box E.' Box E says 'The prize is not in this box.' Only the box containing the prize is telling the truth; all other boxes contain false statements. Which box holds the prize?
You have two identical hourglasses: one measures 7 minutes, and the other measures 4 minutes. Without using any other timekeeping device, how can you measure exactly 9 minutes?
A merchant wants to weigh an exact amount of grain using a balance scale. He has only a 7-pound weight and an 11-pound weight. What is the minimum number of weighings required to measure out exactly 2 pounds of grain?
Three boxes are labeled 'Apples', 'Oranges', and 'Apples and Oranges'. Every single box is labeled incorrectly. You are allowed to pull exactly one fruit from one box of your choice to fix all the labels. Which box do you choose?
Three guards stand before a fortress gate. One always tells the truth, one always lies, and one alternates between truth and lies. You can ask one yes/no question to each guard in any order. What is the minimum number of guards you must question to guarantee identifying the liar?