Calculation Error sum float

I Write This Code:

clc;
clear;
format long
a=1;
for n=1:1:100
    a=a+.1;
end
a

and answer is:

a =

    10.999999999999979

!!!!! Why not: a= 11

How I Can Solve it?

[James Tursa]

See Azzi's link below. But for your particular case this is the decimal equivalent of the closest number to 0.1 in IEEE double format:

>> num2strexact(0.1)
ans =
0.1000000000000000055511151231257827021181583404541015625

You can find num2strexact here:

http://www.mathworks.com/matlabcentral/fileexchange/22239-num2strexact--exact-version-of-num2str-

Answer 1

[Azzi Abdelmalek]

read http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F

[Maha dasra]

How I Can Solve it?

[José-Luis]

1. Use a computer that doesn't use the binary system. There are a few such strange base 10 machines out there.
2. Try variable precision arithmetic. Either with the symbolic toolbox or the excellent vpa from the file exchange.