Why does var a:Double =0.0, a += 0.1 give an inaccurate result?

Question

Kotlin

var a:Double = 0.0
    a += 0.1+0.1+0.1+0.1+0.1+0.1+0.1
   println( a)
//выводит 0.7

If we add another 0.1, it outputs 0.7999999999
then 0.8999999999
then 0.9999999999
then 1.0999999999
Why does it work like this?

Answer 1

https://0.30000000000000004.com/

Answer 2

Because IEEE754