This three-act math task from Dan Meyer brings a classic sibling sharing rule into math class. Dan and his sister were allowed to share one soda when they were younger. Dan’s sister would pour and he would choose. In this brief video, Dan pours soda into two glasses, each with a different shape, begging the questions, “Which one has more soda?” or “Which one should I choose?”

This is a great activity to explore volume and have students talk about which glass holds more – the taller, thinner glass or the shorter, wider one.