## Chemistry: The Central Science (13th Edition)

In part A, the answer showed that there are 386,241,600 meters between the earth and the moon. However, because this problem asks how long it would take to travel to the moon and back, that number must be doubled. $386,241,600 meters\times2=772483200 meters$ The speed of light is given in meters per second already, so there is no need for unit conversion. To find how many seconds it will take, divide 772483200 meters by the speed of light,$3\times10^8 meters per second$ $772483200\div3\times10^8=2.574944 seconds$ Notice, the unit meters cancel out, making the answer in the desired unit, seconds.