Second best question you can ask learners when teaching mathematics
The number one greatest question in your math/numeracy educational arsenal is here.
The second is the following question:
If somebody was going to make a mistake with this, which part would they most likely make the mistake?
Get them to verbalize it, and be very clear.
There are two good reasons for this.
One, the part they identify will most likely be the very part they struggled with.
Two, speech is the key to learning, By getting learners to talk thorough the problem they are actually processing the information.