Anyone knows this sum?

Will qty A be 0 and Qty B be 20?

I used diagonal of a polygon formula for Qty B which is n(n-3) /2

Anyone knows this sum?

Will qty A be 0 and Qty B be 20?

I used diagonal of a polygon formula for Qty B which is n(n-3) /2

The formula will give you all diagonals.

For quantity A, just try to visualise this. Let’s say the octagon has vertices ABCDEFGH. The diagonals from A, namely AD and AF are parallel to one of the sides of the octagon (try to name the vertices and draw the lines). So you can calculate Quantity A from this. Quantity B is just the result of the formula minus quantity A.

I followed your process. For Qty A will it be 8? and Qty B = 20-8 = 12?

Is this correct?

I got 2 diagonals from every point and then realised Diagonal BG which is parallel to DE is getting counted twice as we are counting Diagonal GB is parallel to DE. Hence for Qty A we will have 16-8 =8 or 16/2 =8 . Is this logic correct?

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Correct!

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