About the calculation precise

The precise of calculation has a problem when I add 60.425 with 0.425. The exact value should be 60.85, however I just got 60.8499999..., which affects my following calculation. How I can avoid such problem?

Answer 1

[Walter Roberson]

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

Answer 2

[James Tursa]

For your particular example, none of the values can be represented in IEEE double exactly:

>> num2strexact(60.425)
ans =
6.04249999999999971578290569595992565155029296875e1
>> num2strexact(0.425)
ans =
0.424999999999999988897769753748434595763683319091796875
>> num2strexact(60.425+0.425)
ans =
6.0849999999999994315658113919198513031005859375e1

You can find num2strexact here:

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