“Judge the value of what you have by what you had to gi...

The principle of an opportunity cost does not at first glance seem hard to understand. If you spend half an hour noodling around on Twitter, when you would otherwise have been reading a book, the lost book-reading time is the opportunity cost of the tweeting. If you decide to buy a fancy belt for £100 instead of a cheaper one for £20, the opportunity cost is the £80 shirt you could otherwise have bought. Everything has a cost: whatever you were going to do instead, but couldn’t. [...] ...

 How to Talk Math With Kids

Some simple ways to work numbers into the conversation: Note numbers on signs when you’re walking or driving with children: speed limits and exit numbers, building addresses, sale prices in store windows. Ask children to count how many toys they’re playing with, how many books they’ve pulled out to read, or how many pieces of food are on their plate. Use numbers when you refer to time, dates, and temperatures: how many hours and minutes until bedtime, how many weeks and days until a hol...