Which is greater,

5.15 × 10^-4 or 6.35 × 10^-5

To compare the two numbers, we need to convert them to the same power of 10.

5.15 × 10^-4 = 0.000515
6.35 × 10^-5 = 0.0000635

Since 0.000515 is greater than 0.0000635, 5.15 × 10^-4 is greater than 6.35 × 10^-5.