Once all the pilots had a rule of this kind on the clock, knowing how to do multiplication and division quickly could save your life. Today planes rely on very different technologies but the rule is still useful whenever you want to do operations without having to type. Just line up the two numbers to get quickly tabs on all their multiples. Very useful for travel, just set the exchange rate, for example, if 1 U.S. Dollar is worth 0.75 Euros, how many U.S. Dollars costs a 40 Euros backpack? Just look at the Ruler to see it costs about 53 U.S. Dollars, without doing math! Join the Google+ Community Android Development https://plus.google.com/communities/105153134372062985968 and opt-in https://play.google.com/apps/testing/it.slug.circularsliderule to test new betas!

https://play.google.com/store/apps/details?id=it.slug.circularsliderule&hl=en