TED-Ed: Can you solve the giant iron riddle? - Alex Gendler

The family of giants you work for is throwing a fancy dinner party, but there’s a problem — the elder giant’s favorite shirt is wrinkled! To fix it, you’ll need to power up the giant iron. It needs two batteries to work, but the baby giant mixed the working battery pile with the dead pile. Can you test the batteries so that you get a working pair in seven tries or less? Alex Gendler shows how.