>> reporter: kobliner has been teaching key concepts in economics. she insists kids can learn them young. >> by age three children can understand basic money concepts like exchange or we have to make choices or things have a value and those conversations are important to start when kids are really little. by age seven a lot of those behaviors to do with money, whether it's self-control or delayed gratification-- they start getting set. so those ages three to seven, it's really kind of a nice sweet spot in which parents should be talking to their kids about money. >> reporter: we gathered our own group of kids to try it out. how do people get money to give to the bank? >> my mommy and daddy work to get money for us and they buy milk for me. >> reporter: and you're how old here? another key concept all kids should know, says kobliner: what it means to work for a living, like at the newshour. >> you bring your kid to your office and they see where you work. this woman i know, she said her dad would leave every morning when she was little with a newspape

best-selling author beth kobliner is here to share secrets from her new book called "make your kid a the most important thing parents should know? before we get to our lesson what's the most important thing they should know? >> the important thing, you have to start early and start when your kid is 3 because they understand basic concepts like exchange and like -- >> already failing. >> but by 7, some of those habits are already set according to research so it's good but it's never too late. >> all right, so we have some questions for everybody. we'll put you guys to the test and hopefully teach you all something in the process and we'll say a few statements then you tell me if you think they're true and false and beth will tell you what she has to say about the answers. numero uno, handing cash to your kids may make them spend le. true or false, michael, kate, amy. okay, what do you think? >> beth. >> i have to say true is correct. >> oh. >> i was hoping that. >> the idea is when you give your -- when people use cash they spend less than when they use credit cards or debit cards, in