MYSQL do wrong math with strings

Question

Simple sql code gives strange result:

select '0.29'*100;

Result: 28.999999999999996

Another one:

select '0.28'*100;

Result: 28.000000000000004

What's going on? Is it a bug?

I couldn't find any other number that behaves like that.

Answer 1

Double is 32-bit, and when you output it's an int, it's 16 bit, and of course there's a loss of precision