Do more people in a boat help or do they slow it down? Image: Yanid.

We're getting very excited about the medals that will be awarded in canoeing and kayaking over the next three days. But here's a question: does having lots of paddlers helps or slow the boat down? The kayak with two paddlers has twice as many "engines" to power it, but it also has twice as much weight to drag through the water. Which is the dominant factor? It's something we should be able to work out using some relatively straight-forward maths. And indeed we can — you can find the answer here.