floating-point in Rust

Float data type in Rust can be classified as f32 and f64. The f32 type is a single-precision float, and f64 has double precision. The default type is f64.
```
   let result = 10.00;        //f64 by default
   let interest:f32 = 20.00;
   let cost:f64 = 30.001;  //double precision
```