Here's a good example I just came across of why it's useful to be able to do approximate multiplication in your head (perhaps even while intoxicated): http://ne

Here's a good example I just came across of why it's useful to be able to do approximate multiplication in your head (perhaps even while intoxicated): http://news.nationalpost.com/full-comment/robyn-urback-sorry-about-your-1000-uber-bill-but-the-internet-isnt-idiot-proof http://news.nationalpost.com/full-comment/robyn-urback-sorry...