Pi(e) Roll-top Backpack – Royal Institution
£45
Product description from their website:
I don't know about you, but we're a bit peckish... Enjoy a tasty slice of pi(e) with this new mathematics inspired design! Pi is one of the most well-known mathematical constants and is the ratio of a circle’s circumference to its diameter. For any circle, the distance around the edge is a little more than three times the distance across. Buying from us directly supports our charitable activities, such as support to engage with science for disadvantaged schools.