In one of your many trips to the Sahara deserts, your camel dies. Without camel or any drinking water, you long to get home as soon as possible. Lucky for you, a local passes by, with a camel, and you ask him for a ride to the nearest city, which is 7 miles away. He agrees, but in return, he asks for that big rectangular gold piece you're holding in your hand.
The problem is - there is no trust between you two. You offer to give it to him after the ride, and he doesn't agree. You agree on you giving him one seventh of the gold piece for every mile passed, after the mile was passed. Now, we arrive to the real problem - all you have is a saw, that can cut the gold piece only twice (after that it will break), and a ruler. How will you cut the gold piece so that the agreement works out?