Calculate the length of the side of the Triangle marked by x.

This would be a question that would test the students understanding of Pythagoras' Theorem. When teaching this before I have often found that students are scared of thee questions because of the name, so I would begin by making clear that this is a very simple exercise that just involves using one formula: a^2 + b^2 = c^2.

Then to tackle the problem, I would have drawn the relevant right-angled triangle using the whiteboard with the unknown side marked with an x. Then I would ask them which sides of the triangle represented wich part of the formula above to see how much they knew and where their confusion lies. After that I would explain that in this formula, c^2 always represents the longest side of a right angled triangle; known as the hypotenuse. I would then proceed to work out the question with them explaining each step as I go along.

The answer to the this one, as I can't draw on the whiteboard yet is 15 and if required I will show the drawing of the triangle through the webcam for the interview.