Fran and Dave explain areas and the formulae for different shapes in this video aimed at Key Stage 4 maths classes.
Fran's friend wants to know how much it will cost to re-tile her bathroom and Dave is promised a homemade cookie if he is able cost it.
Dave wants the largest cookie, but to work out which cookie is the biggest, he needs to work out their surface areas.
As Dave arrives at the house his first task is to work out the area of the walls to be covered by tiles, a job that is complicated by a mirror and windows.
Separately Fran works out the area of the walls, and then changes the figure when her friend decides she wants a circular and then arched mirror.
Meanwhile Dave works out the cost of re-tiling the bathroom, and is rewarded with the circular cookie, which he worked out was largest.
When the cookie arrives it is considerably smaller than he expected, does this mean he got the formula for the area of a circle wrong?