I <i>kind of</i> agree. Most tricks are just a bit of fun. But some of the time when you need to do some mental arithmetic in the real world you&#x27;re not actually looking for the right answer. It&#x27;s more about estimating things. No one really needs to be able to multiply a pair of two digit numbers in their head, but if you&#x27;re at a hardware store and you need to figure out how much paint to buy, being able to estimate the area of a wall quickly having a trick up your sleeve that gets you most of the way is very handy indeed.<p>Also, a lot of the time these sorts of things aren&#x27;t going to be used directly, but are more of an indicator of what to type in to a calculator. Knowing how to do something in your head <i>informs</i> how you do it on a calculator even if you don&#x27;t actually use the trick yourself. A lot of people who are bad at maths don&#x27;t even know where to start, so having a device to do the actual sums doesn&#x27;t help them.