while teaching xth class CBSE mathematics i have noticed that atleast 30- 40% of the time is spent by the teacher in writing on the board ( black/white) while explaining a concept. During this time the eye-contact with the student is missed. And this could lead to wavering of concentration especially amongst not so attentive students. And to bring them back into the loop would be very time consuming disturbing the other committed students.

But this time can be reduced – can’t be fully avoided – with the help of Power Point presentations. All concepts, the problem itself, and the explanation of a solution can be pre-arranged in slide form which can be great teaching aid.

However, some unforeseen issues/explanations that may crop up resultant of student queries may however require improvised answer on the spot, for whcih the teacher need to take the help of black/white board as the case be.
But a significant amount of time can be saved.

CBSE Notes 2010