How to Be Good at Maths

It's like whenever I'm in the supermarket and you see prices of things that are allegedly on offer. And your book, they all just lie about the price. They just say it's on sale like 50%. The trick is in the comparison that they give you. But there's another supermarket down the road where if you buy six bottles at once, you get 25% off. You just need to have like a shopping trolley. He says he never studied economics in school but has learned so much from his colleagues.