Example 1B.5 in textbook

[Guzman_1J]

For Example 1B.5 in textbook Using the uncertainty principle, when grams and mm/s is being converted into SI units they are multiplied by 2 once they have been converted but the textbook does not explain why. Does anybody understand this problem? I know how we are supposed to use the equation, it's just multiplying mass and speed by two once they have been converted to the right SI units that I don't understand.

[Rachel Yu 1G]

The two comes from the given equation ΔpΔx = 1/2h which is converted into Δx = h/2mΔv. The textbook then plugs in the given values to the latter equation, which is where the 2 comes from. While the mass (m) and uncertainty in speed (Δv) values are converted within the equation, the 2 value remains there because it is part of the plugged-in the equation. Basically, the 2 has nothing to do with conversion, it is just part of the given equation. I also found it weird that the textbook didn't convert the values to SI units before plugging the values in.