why output of this code is 0.30000000000000004 instead of 0.3

Question

https://code.sololearn.com/c79jOIvcseLP

Answer 1

This is a good question indeed.

The reason of the error is that computers store decimals in binary.

For example, 0.5 is 0.1(binary), just like 4 is 100(binary).

For 0.75, 0.25, 0.125, they can be saved as exact value.

For 0.3, it is saved as an approximation.

For more explicit explanation, I would recommend Anna's explanation to Kenny Wong.

https://www.sololearn.com/Discuss/1477626/?ref=app

Good job in thinking deep about these findings. You are on the right track. Keep up 💪

Answer 2

js is not precise whan working with decimals and long numbers, you can use toFixed(1) to fix it to one decimal

console.log((0.1+0.2).toFixed(1))

for 2 decimal like 0.30 use toFixed(2) and so on..
I wraped it in () to group them and apply toFixed to sum of two decimal numbers.

Answer 3

I want to know how it calculate that answer will be equal to 0.30000000000000004 not for example 0.30000000000000013.
it's not just for JS.
in Python this problem also exists:
https://code.sololearn.com/cH3DIz79mKe7