# The coin flip conundrum - Po-Shen Loh

658,261 Views

TEDEd Animation

## Let’s Begin…

When you flip a coin to make a decision, there's an equal chance of getting heads and tails. What if you flipped two coins repeatedly, so that one option would win as soon as two heads showed up in a row on that coin, and one option would win as soon as heads was immediately followed by tails on the other? Would each option still have an equal chance? Po-Shen Loh describes the counterintuitive math behind this question.

Suppose that you were playing an abstract board game similar to the heads/tails game, except that it had four positions in this order: Start, B, C, and End. Suppose that on each turn, from any position except for End, there is a 50% chance of staying at that position and a 50% chance of moving to the next position. What is the average number of turns to move from Start to End?

TED-Ed Animations feature the words and ideas of educators brought to life by professional animators. Are you an educator or animator interested in creating a TED-Ed Animation? Nominate yourself here »

## Meet The Creators

• Educator Po-Shen Loh
• Director Mimi Chiu
• Script Editor Eleanor Nelsen
• Producer Aaron Augenblick
• Animator Mimi Chiu
• Collaborator Andrea Janov , Zach Nelkin, Mark Paulson
• Associate Producer Elizabeth Cox, Jessica Ruby
• Content Producer Gerta Xhelo
• Editorial Producer Alex Rosenthal