Most calculators are simply not good at properly calculating multiplication with infinitely repeating decimals. You are correct that 33.33333…(repeating) should be 100 when it’s multiplied by 3. And on a sufficiently sophisticated calculator, it would be. However, most calculators are not properly...
Set the repeating fraction equal to x. For example, if your infinite decimal is 0.18232323... you would write x=0.182323... Determine the repeating length of the decimal. The repeating length is the number of digits in the repeating pattern. For example, 0.182323... has a repeating length ...