Which of these numbers are less than 8.1 × 10^-8? a)8.2 × 10^-8 b)7.3 × 10^-5 c)9.2 × 10^-9 d)3.4 × 10^-10

8.1 x 10^-8
When going in the negative direction, the further left you go, the smaller the number.
These number would order smallest to largest as:
3.4x10^-10
9.2x10^-9
8.1x10^-8
8.2x10^-8
7.3x10^-5

Letters C & D