Precalculus (6th Edition) Blitzer

$7.25\times10^{-3}$
The original number is .00725. To be in scientific notation, the decimal must come after the first number. To do that we need to move it (the decimal place) three digits over to the right. By doing that, we multiply it by $10^3$, which is the same thing as dividing it by $10^{-3}$, so to keep the value the same we must multiply by $10^{-3}$, which gives us $7.25\times10^{-3}$.