Unit pricing, best buys, call it what you will, this topic is great because it is relatable, practical and prompts rich conversation. This week I started a lesson with a lower ability Year 10 class with this image: After some hesitations one student piped up: "Do 80 divided by $5.39!" I wrote on the whiteboard 80/5.39 and the students told me confidently the answer was 14 cents. Me: "How do we know this is correct? Is there a way we can check?" After some discussion we figured out we could multiply 80 by 14 cents which they told me was $11.20. Me: "Are we happy with this?" Students: "I guess." Me: "So if you take this packet of lollies to the checkout and they charge you $11.20 you are ok with that?" One Student: "You're gettting scammed!" I was amazed. The students took quite some time thinking through how the shop keeper were cheating the customer. Eventually they were convinced that maybe the maths was wrong. It was d...