A ruler has 4 sealed bottles of juice, but exactly 1 bottle contains deadly poison. The ruler has 2 taste-testers. The poison takes exactly 1 hour to take effect. How can the ruler identify the exact poisoned bottle after 1 hour using only these 2 testers?
Tester 1 drinks from bottles 1 and 2; Tester 2 drinks from bottles 2 and 3
If only Tester 1 falls ill, Bottle 1 is poisoned. If both Testers fall ill, Bottle 2 is poisoned. If only Tester 2 falls ill, Bottle 3 is poisoned. If neither Tester falls ill, Bottle 4 is poisoned.
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: Hard. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
More logic riddles
An island has 100 inhabitants who all have either blue eyes or brown eyes, but nobody knows their own eye color. They are forbidden from speaking about eye color. Every day at noon, a ferry arrives to take away anyone who has deduced their own eye color. A visitor arrives and publicly announces: "At least one person here has blue eyes." If exactly 3 people on the island have blue eyes, on which day will they leave?
A merchant has five sacks of gold coins weighing 10, 11, 12, 13, and 14 pounds, though they all look identical. One sack contains counterfeit coins that weigh exactly one pound less than genuine coins. Using a digital scale only once, how can the merchant identify the counterfeit sack?
The rabbit is bigger than the bunny, and the chick is bigger than the rabbit. Which one is the middle size?
Three runners—Leo, Max, and Sam—each wear a shirt of a different color: Red, Blue, or Green. Max is not wearing the Red shirt. The runner in the Blue shirt finished ahead of Sam. Leo is wearing the Green shirt. What color shirt is Max wearing?
Three boxes are labeled 'Apples', 'Oranges', and 'Apples and Oranges'. Every single box is labeled incorrectly. You may draw just one piece of fruit from one box to correct all the labels. Which box do you choose?
A detective who was tall enough to look out a second-story window noticed a man lying dead on the pavement below, with a closed window right beside him and a heavy book clutched in his hand. The detective immediately declared it was murder, not suicide. How did he know?