Abike rider rides at an average of 12 m/s for 30 minutes. how many km can the rider travel in that time? show your work.
(what it means by that time? i meant the 30 min just to let you guys know^^)

(a) calculate the number of electrons in a small, electrically neutral silver pin that has a mass of 10.0 g. silver has 47 electrons per atom, and its molar mass is 107.87 g/mol. (b) imagine adding electrons to the pin until the negative charge has the very large value 1.00 mc. how many electrons are added for every 109 electrons already present