Creating Calculating Android Apps, using MIT App Inventor 2

How to create Android Calculating Apps using the "MIT App Inventor 2" website. It's free and you won't need to learn any programming languages!
This book covers Apps that will work out Mathetical Solutions given 1 or more input from the user.
You'll be able to create Apps to work out any mathematical equation/s you want it to:
Areas of circles, triangles, rectangles, etc.
Areas and Volumes of cylinders, spheres, prisms, etc.
Gear ratios
Take 2 prices for 2 different amount of something and work out which is the cheaper
The differences on rolling height, speeds or overall gearing of 2 tyres.
Amounts of ingredients for a different number of portions, if that's what you need.

And the list goes on.

You'll learn how to;
Convert or Calculate a single number or multiple numbers.
Give the user the choice of say 2 out of 5 possible inputs to work out the others.
Get the App to flag any Errors the User puts in.
How to tell the user where they are going wrong.
How to create and use variables.
Allow the user to choose to select from preset inputs or their own.
Allow the user to change the accuracy of the output displayed.(Decimal Places 0 - 4 or 6 or whatever you set)
Create different looks to your Apps.
Control the version of Apps you might have created.