Adding 0.* to x result isnt correct

hey.
This:


for (var i=0; i<10; i++){
	symb.x += 0.4;
	trace(symb.x);
}

Where symb is an movieclip on x 0 and y 0.
the result of trace is:

0.4
0.8
1.2
1.6
2
2.4
2.8
**3.15** what happens here
3.55
3.95
4.35

This drives me crazy! if i extend the for loop to do 100 loops, it happens at moer places. Anybody, please!