Riddle:
One afternoon, Cara came home and found that her favorite vase had been shattered. The woman questioned her three kids—Ali, Gia, and Joe. Ali said, "It was Gia!". Gia kept silent, and so did Joe. Assuming that the culprit tells the truth, who shattered Cara's vase?

Answer: It was Joe. If Ali is telling the truth, then he's the culprit. But that would make Gia the culprit, too, which would then create a paradox. Therefore, Ali is lying, and Joe is the culprit by default.

Riddle:
Three hens lay three eggs in three days. How many eggs do 15 hens lay in 15 days?

Answer: If three hens lay three eggs in three days, then one hen lays one egg in three days. In 15 days, one hen will lay five eggs. Therefore, 15 hens will lay 75 eggs in 15 days.

Riddle:
Your grandma baked three cupcakes for you, and she's letting you eat one of them. She knows that you don't like strawberries, so she lines the cupcakes in a row and tells you, "The orange cupcake is not in the middle. And the apple cupcake is not next to the orange cupcake,". Which cupcake is strawberry-flavored?

Answer: The orange cupcake is not in the middle, and the apple cupcake can't be in the middle either because it would contradict your grandma's second statement. Therefore, the orange and apple cupcakes are on the ends, and the strawberry cupcake is in the middle.

Riddle:
Two ladies were detained by security officers at an airport–one of whom claimed to be a computer scientist, and one of whom claimed to be a geographer. One of them was secretly a smuggler! A security officer asked the supposed computer scientist, "Do you know about the Gava computer program?". The woman answered, "Do you mean Java?". The security officer then asked the supposed geographer, "Have you ever been to the capital of Spain, that is, Granada?". The geographer said, "Yes! It's a beautiful city!". Who was the smuggler?

Answer: The capital of Spain is Madrid, not Granada. If the second woman was really a geographer, she would know this; she must be the smuggler!

Riddle:
A butterfly flies to a rock in the middle of a huge lake and stops to rest. If it swims North, it's five minutes to the mainland. If it swims East, it's four minutes to the mainland. If it swims South, it's three minutes to the mainland. And if it swims West, it's two minutes to the mainland. In which direction should the butterfly swim?

Answer: The butterfly shouldn't swim in any direction because butterflies don't swim; they fly!

Riddle:
One day, down at the South Pole, five penguins and twice as many polar bears got onto a train. The train was headed to another station that was 15 minutes away from where it was initially. What is wrong with this story?

Answer: Polar bears live at the North Pole, while penguins live at the South Pole. They can't coexist at the same Pole.

Riddle:
A green apple costs $1, a red apple costs $2, and a blue apple costs $3. If you have $3, but only two bills, what apples can you buy?

Answer: There are two solutions; you can either buy one green apple and one red apple using a $1 and a $2 (yes, $2 bills are a thing), or you can buy three green apples using the same two bills. You could have bought one blue apple using those bills, but blue apples don't exist!

Answer: The ambiguity of this riddle means that the answer could be either two or three. But the real answer is three because you have to follow the order of operations (half of two is one, and one plus two is three).