If one thing can be done in m ways and another thing can be done in n ways, the two things can be done in mn ways. Example: A restaurant has 5 appetizers, 8 beverages, 9 entrees, and 6 desserts on the ...

"Our study is new because we have shown that babies, long before they can start to count themselves, can recognise a fundamental principle of counting: that every single object must be counted for ...