5.100 x 10⁻³ = 5.100 x 0.001
= 0.005100 (shift the decimal point for 5 by 3 units left)
Alternatively, because 10⁻³ = 1/1000, therefore
5.100 x 10⁻³ = 5.1/1000
0.0051
---------------
1000 | 5.100
5000
-------------
1000
1000
This yields the same result.
Answer: b. 0.005100
