To compare the two numbers, we can look at their decimal representations.
0.0000635 is equivalent to 635 × 10^(-6). 0.000456 is equivalent to 456 × 10^(-3).
Now let's convert 0.0000635 to a number with the same number of decimal places as 0.000456:
0.0000635 = 0.0000635 (this is already in the required form)
0.000456 = 0.000456 (this is also in the required form)
Now, we can compare: 0.0000635 is less than 0.000456.
Thus, the correct symbol is:
0.0000635 < 0.000456.