I remember when we asked our math teacher Mr. Adhikari about what is 'i'. He didnt knew. But he spent about a week researching and got an answer that an 8th grader would understand. We loved it. AND THERE IS ONE MORE THING……

Accept when you don't know When you do not know accept it. You can tell them later. You can setup a forum for your class where students put up their problems and you can answer them in your free time at your ease. Students can also solve each other's problems using the forum.   You will come of as someone they can trust.