Can you solve the prisoner hat riddle? - Alex Gendler (Level 1)

Ten people are captured by aliens. The aliens want to eat them, but they will let the humans go if they pass a test. The people must stand in a line. Each person wears a black or white hat. They can see the hats in front of them, but they cannot see their own hat. Starting from the back, each person must guess their color. If nine people answer correctly, everyone survives. The group makes a smart plan using math. The person at the back counts the black hats in front of him. If he sees an odd number, he says "Black." If he sees an even number, he says "White." This tells the other people the secret code. The first person might be wrong about his own hat, but his answer helps everyone else. The other nine people listen and count the hats they see. This helps them know their own color for sure. Because they work together, the aliens let them go.