9 dived by 3 = 3
so he surfed for 3 hours = 1/3 of 9
and there are 6 hours left
so he spent 6 hours building a sandcastle
The Order of magnitude for the population of the world is not five
There are 13 protons because the atomic number (the number in the top left corner) represents the number of protons. Then, to find the number of neutrons, you take the number of protons and subtract it from the atomic mass (the number on the bottom) when it is rounded. The number of electrons is the same as the protons when the atom is neutral