Multiplication int and float(double) in JavaScript [duplicate]

Answer 1

It's a rounding error. You may want to round your number to a fixed amount of digits, like this:

parseFloat((your_number).toFixed(2));

Answer 2

Unfortunately this happens in any language using floating point arithmetic. It's an artifact arising when floating point operations are encoded into binary, operations performed, and decoded from binary to report the answer in a form you'd expect.

Depending on what you want to do with the output, you can call a round()-like function to round to a number of decimal places or compare the output to a value using a (small) number called a tolerance. E.g. two numbers are considered equal if their absolute difference is less than this tolerance.