Circular Slide Ruler is an app that is designed to help you quickly multiply and divide by using your fingers to touch the screen. There are no numbers or letters to type, so you can quickly calculate all kinds of different numbers and multiples. All you need to do is touch the screen to multiply or divide by a number. You can even use it for mathematical operations that require a lot of numbers, like multiplication, division, and more. 

It is also very useful for travelers because you can set the exchange rate for different currencies and calculate the cost of an item or a service.